FIXED INCOME SHARES: SERIES R

Fixed Income SHares: Series R

Summary Prospectus

April 30, 2026

Series	R
Ticker	FXIRX

Before you invest, you may want to review the Portfolio’s prospectus, which, as supplemented, contains more information about the Portfolio and its risks. You can find the Portfolio’s prospectus, reports to shareholders, and other information about the Portfolio online at www.pimco.com/FISH. You can also get this information at no cost by calling 1-800-927-4648 or by sending an email request to piprocess@sscinc.com. The Portfolio’s prospectus and Statement of Additional Information, both dated April 30, 2026, as supplemented, are incorporated by reference into this Summary Prospectus.

Investment Objective

The Portfolio seeks maximum real return, consistent with preservation of real capital and prudent investment management.

Fees and Expenses of the Portfolio

The table below describes the fees and expenses you pay if you buy, hold and sell shares of the Portfolio. You may pay other fees, such as brokerage commissions and other fees to financial intermediaries, which are not reflected in the table and example below.

Shareholder Fees (fees paid directly from your investment):

None

Annual Portfolio Operating Expenses (expenses that you pay each year as a percentage of the value of your investment):

	FISH: Series R
Advisory Fees(1)	0.00%
Other Expenses(2)	3.92%
Total Annual Portfolio Operating Expenses	3.92%

The Portfolio does not pay an advisory fee to Pacific Investment Management Company LLC (“PIMCO”) under the Investment Advisory Contract between PIMCO Managed Accounts Trust (the “Trust”) and PIMCO (the “Investment Advisory Contract”). However, the Portfolio is an integral part of “wrap-fee” programs, including those sponsored by investment advisers and broker- dealers unaffiliated with the Portfolio or PIMCO. Participants in these programs pay a “wrap” fee to the sponsor of the program. You should read carefully the wrap-fee brochure provided to you by the sponsor or your investment adviser. The brochure is required to include information about the fees charged to you by the sponsor and the fees paid by the sponsor to PIMCO and its affiliates. You pay no additional fees or expenses to purchase shares of the Portfolio.

“Other Expenses” include interest expense of 3.92%. Interest expense is borne by the Portfolio separately from the management fees paid to PIMCO. Excluding interest expense, Total Annual Portfolio Operating Expenses are 0.00%.

Example. This Example is intended to help you compare the cost of investing in shares of the Portfolio with the costs of investing in other mutual funds. The Example assumes that you invest $10,000 in shares of the Portfolio for the time periods indicated, and then hold or redeem all of your shares at the end of those periods. The Example also assumes that your investment has a 5% return each year and the Portfolio’s operating expenses remain the same. Although your actual costs may be higher or lower, the Example shows what your costs would be based on these assumptions.

	1 Year	3 Years	5 Years	10 Years
FISH: Series R	$394	$1,195	$2,014	$4,138

Portfolio Turnover

The Portfolio pays transaction costs when it buys and sells securities (or “turns over” its portfolio). A higher portfolio turnover rate may indicate higher transaction costs and may result in higher taxes when Portfolio shares are held in a taxable account. These costs, which are not reflected in the Annual Portfolio Operating Expenses or in the Example table, can adversely affect the Portfolio’s performance. During the most recent fiscal year, the Portfolio’s portfolio turnover rate was 157% of the average value of its portfolio.

Principal Investment Strategies

The Portfolio seeks to achieve its investment objective by normally investing at least 80% of its net assets (plus borrowings made for investment purposes) in a portfolio of U.S. and foreign fixed income instruments including (but not limited to): inflation-indexed bonds issued by both U.S. and non-U.S. governments and corporations, including Treasury Inflation Protected Securities (“TIPS”); corporate debt securities of U.S. and non-U.S. issuers, including convertible securities and corporate commercial paper; obligations issued or guaranteed by the U.S. Government, its agencies and instrumentalities; obligations of non-U.S. governments or their subdivisions, agencies and government sponsored enterprises; obligations of international agencies or supranational entities; debt securities issued by states or local governments and their agencies, authorities and other instrumentalities; mortgage-related and other asset-backed securities including collateralized bond obligations (“CBOs”), collateralized loan obligations (“CLOs”), other collateralized debt obligations (“CDOs”) and other similarly structured securities; floating and variable rate debt instruments; structured notes, including hybrid or “indexed” securities and event-linked bonds; loan participations and assignments; delayed funding loans and revolving credit facilities; bank certificates of deposit, fixed time deposits and bankers’ acceptances; repurchase agreements and reverse repurchase agreements; and derivative instruments that have economic characteristics similar to the securities referenced above.

In pursuing its investment objective of real return, the Portfolio ordinarily expects to invest a substantial portion of its assets in inflation-indexed bonds of various maturities issued by U.S. and non-U.S. governments, their agencies or instrumentalities, and corporations. Certain securities issued by U.S. Government-sponsored entities may not be backed by the full faith and credit of the U.S. Government. “Real return” equals total return less the estimated cost of inflation, which is typically measured by the change in an official inflation measure. Inflation-indexed bonds are fixed income securities that are structured to provide protection against inflation. The value of the bond’s principal or the interest income paid on the bond is adjusted to track changes in an official inflation measure. The U.S. Treasury uses the non-seasonally adjusted Consumer Price Index for All Urban Consumers as the inflation measure. Inflation-indexed bonds issued by a foreign government are generally adjusted to reflect a comparable inflation index, calculated by that government.

PIMCO Managed Accounts Trust | Summary Prospectus

Fixed Income SHares: Series R

The Portfolio invests primarily in investment grade securities, but may invest up to 20% of its assets in high yield securities (“junk bonds”) rated B or higher by Moody's Ratings (“Moody’s”), or equivalently rated by Standard & Poor’s (“S&P”) or Fitch Ratings, Inc. (“Fitch”) or, if unrated, determined by PIMCO to be of comparable quality to securities so rated (except that within such 20% limitation, the Portfolio may invest in mortgage-related securities rated below B). In the event that ratings services assign different ratings to the same security, PIMCO will use the highest rating as the credit rating for that security. The Portfolio may invest, subject to applicable law, without limit in foreign (non-U.S.) currencies, securities denominated in foreign (non-U.S.) currencies, and U.S. dollar denominated securities of foreign issuers. The Portfolio may invest without limit in investment grade sovereign debt denominated in the relevant country’s local currency with less than 1 year remaining to maturity (“short-term investment grade sovereign debt”), including short-term investment grade sovereign debt issued by emerging market issuers. The Portfolio may invest up to 20% of its total assets in securities of issuers economically tied to “emerging market” countries other than investments in short-term investment grade sovereign debt issued by emerging market issuers, where as noted above there is no limit.

The Portfolio may invest in instruments of any maturity. The average portfolio duration of the Portfolio is expected to vary and may range anywhere from relatively short (e.g., less than two years) to relatively long (e.g., more than ten years) based on PIMCO’s forecast for interest rates.

The Portfolio may invest without limit in derivative instruments, such as options, futures contracts or swap agreements, which may relate to fixed income securities, interest rates, currencies or currency exchange rates, commodities, real estate and other assets, and related indices. Although the Portfolio may invest in derivatives of any kind, it expects to invest in futures contracts, swaps and forward foreign currency contracts and to write (sell) put and call options on securities for hedging, risk management or other purposes, including for the purpose or having the effect of creating leverage. The Portfolio may lend its securities to brokers, dealers and other financial institutions to earn income. The Portfolio may, without limitation, seek to obtain market exposure to the securities in which it primarily invests by entering into a series of purchase and sale contracts or by using other investment techniques (such as buy backs or dollar rolls).

The Portfolio will not change its policy to, under normal circumstances, invest at least 80% of its net assets (plus the amount of any borrowings for investment purposes) in U.S. and foreign fixed income instruments unless the Portfolio provides shareholders with the notice required by Rule 35d-1 under the Investment Company Act of 1940, as it may be amended or interpreted by the Securities and Exchange Commission (the “SEC”) from time to time (the “1940 Act”).

Principal Risks

It is possible to experience losses on an investment in the Portfolio. The principal risks of investing in the Portfolio, which could adversely affect its net asset value, yield and total return, are listed below.

Interest Rate Risk: the risk that fixed income securities will fluctuate in value due to changes in interest rates; a portfolio with a longer average portfolio duration will be more sensitive to changes in interest rates than a portfolio with a shorter average portfolio duration. Factors such as government and central bank policy, inflation, the economy, and the market for bonds can impact interest rates and yields

Credit Risk: the risk that the Portfolio could experience losses if the issuer or guarantor of a fixed income security, the counterparty to a derivative contract or a repurchase agreement, a borrower of portfolio securities, or the issuer or guarantor of collateral, is unable or unwilling, or is perceived (whether by market participants, rating agencies, pricing services or otherwise) as unable or unwilling, to meet its financial obligations

Market Risk: the risk that the value of securities owned by the Portfolio may fluctuate, sometimes rapidly or unpredictably, due to a variety of factors affecting securities markets generally or particular industries or sectors

Foreign (Non-U.S.) Investment Risk: the risk that investing in foreign (non-U.S.) securities may result in the Portfolio experiencing more rapid and extreme changes in value than a portfolio that invests exclusively in securities of U.S. companies, due to smaller or less developed markets, differing financial reporting, accounting, corporate governance and auditing standards, increased risk of delayed settlement of portfolio transactions or loss of certificates of portfolio securities, and the risk of unfavorable U.S. or foreign government actions, including nationalization, expropriation or confiscatory taxation, currency blockage, political changes, diplomatic developments, trade restrictions (including tariffs) or the imposition of sanctions and other similar measures. Foreign securities may also be less liquid and more difficult to value than securities of U.S. issuers

Mortgage-Related and Other Asset-Backed Securities Risk: the risks of investing in mortgage-related and other asset-backed securities, including interest rate risk, extension risk, prepayment risk and credit risk. The Portfolio may invest in any tranche of mortgage-related and other asset-backed securities, including junior and/or equity tranches (to the extent consistent with the Portfolio's guidelines), which generally carry higher levels of the foregoing risks

Emerging Markets Risk: the risk of investing in emerging market securities, primarily increased foreign (non-U.S.) investment risk

Focused Investment Risk: the risk that, to the extent that the Portfolio focuses its investments in a particular sector, it may be susceptible to loss due to adverse developments affecting that sector. Furthermore, the Portfolio may invest a substantial portion of its assets in companies in related sectors that may share common characteristics, are often subject to similar business risks and regulatory burdens, and whose securities may react similarly to market developments, which will subject the Portfolio to greater risk. The Portfolio also will be subject to focused investment risk to the extent that it invests a substantial portion of its assets in a particular issuer, market, asset class, country or geographic region

2 Summary Prospectus | PIMCO Managed Accounts Trust

Summary Prospectus

Derivatives Risk: the risk of investing in derivative instruments (such as forwards, futures, options, swaps and structured securities) and other similar investments, including leverage, liquidity, interest rate, market, counterparty (including credit), operational, legal and management risks, and valuation complexity. Changes in the value of a derivative or other similar investment may not correlate perfectly with, and may be more sensitive to market events than, the underlying asset, rate or index, and the Portfolio could lose more than the initial amount invested. Derivatives used for hedging or risk management may not operate as intended or may expose the Portfolio to additional risks. Changes in the value of a derivative or other similar instrument may also create margin delivery or settlement payment obligations for the Portfolio. The Portfolio’s use of derivatives or other similar investments may result in losses to the Portfolio, a reduction in the Portfolio’s returns and/or increased volatility. Non-centrally-cleared over-the-counter (“OTC”) derivatives or other similar investments are also subject to the risk that a counterparty to the transaction will not fulfill its contractual obligations to the other party, as many of the protections afforded to centrally-cleared derivative transactions might not be available for non-centrally cleared OTC derivatives or other similar investments. The primary credit risk on derivatives or other similar investments that are exchange-traded or traded through a central clearing counterparty resides with the Portfolio's clearing broker or the clearinghouse. Changes in regulations relating to a registered fund’s use of derivatives and related instruments could potentially limit or impact the Portfolio’s ability to invest in derivatives, limit the Portfolio’s ability to employ certain strategies that use derivatives or other similar investments and/or adversely affect the value of derivatives or other similar investments and the Portfolio’s performance

Liquidity Risk: the risk that a particular investment may be difficult to purchase or sell and that the Portfolio may be unable to sell investments at an advantageous time or price or achieve its desired level of exposure to a certain sector. Liquidity risk may result from the lack of an active market, reduced number and capacity of traditional market participants to make a market in fixed income securities, and may be magnified in changing interest rate environments or other circumstances where investor redemptions from fixed income funds may be higher than normal, causing increased supply in the market due to selling activity. The liquidity of the Portfolio’s shares may be constrained by the liquidity of the Portfolio’s portfolio holdings

Management Risk: the risk that the investment techniques and risk analyses applied by PIMCO will not produce the desired results and that actual or potential conflicts of interest, legislative, regulatory or tax restrictions, policies or developments may affect the investment techniques available to PIMCO in connection with managing the Portfolio and may cause PIMCO to restrict or prohibit participation in certain investments. There is no guarantee that the investment objective of the Portfolio will be achieved

High Yield Risk: the risk that high yield securities and unrated securities of similar credit quality (commonly known as “junk bonds”) are subject to greater levels of market, credit, call and liquidity risks. High yield securities are considered primarily speculative by rating

agencies with respect to the issuer’s continuing ability to make principal and interest payments, and their values may be more volatile than higher-rated securities of similar maturity

Currency Risk: the risk that foreign (non-U.S.) currencies may fluctuate in value relative to the U.S. dollar, which can affect the value of the Portfolio’s investments in foreign (non-U.S.) currencies or in securities that trade in, and receive revenues in, or in derivatives that provide exposure to, foreign (non-U.S.) currencies

Leveraging Risk: the risk that certain transactions of the Portfolio, such as reverse repurchase agreements, loans of portfolio securities, and the use of when-issued, delayed delivery or forward commitment transactions, and derivative instruments, may give rise to leverage, magnifying gains and losses and causing the Portfolio to be more volatile than if it had not been leveraged. This means that leverage entails a heightened risk of loss. The use of leverage may also increase the Portfolio’s sensitivity to interest rate changes and other market risks

Issuer Risk: the risk that the value of a security may decline for reasons related to the issuer, such as management performance, changes in financial condition or credit rating, financial leverage, reputation or reduced demand for the issuer’s goods or services

Turnover Risk: the risk that high levels of portfolio turnover may increase transaction costs and taxes and may lower investment performance

Municipal Securities Risk: the risk that investing in municipal securities subjects the Portfolio to certain risks, including variations in the quality of municipal securities, both within a particular classification and between classifications. The rates of return on municipal securities can depend on a variety of factors, including general money market conditions, the financial condition of the issuer, general conditions of the municipal bond market, the size of a particular offering, the maturity of the obligation and the rating of the issue

Inflation/Deflation Risk: the risk that the value of assets or income from a Portfolio's investments will be worth less in the future as inflation decreases the value of payments at future dates. As inflation increases, the real value of a Portfolio's investments could decline. Inflation rates may change frequently and significantly as a result of various factors, including unexpected shifts in the domestic or global economy or changes in fiscal or monetary policies (or the expectation of such changes). Deflation risk is the risk that prices throughout the economy decline over time. Deflation may have an adverse effect on the creditworthiness of issuers and may make issuer default more likely, which may result in a decline in the value of a Portfolio's investments

Sovereign Debt Risk: the risk that investments in fixed income instruments issued by sovereign entities may decline in value as a result of default or other adverse credit events resulting from an issuer’s inability or unwillingness to make principal or interest payments in a timely fashion

Collateralized Loan Obligations Risk: the risk that investing in collateralized loan obligations (“CLOs”) and other similarly structured

April 30, 2026 | SUMMARY PROSPECTUS 3

Fixed Income SHares: Series R

investments exposes the Portfolio to heightened credit risk, interest rate risk, liquidity risk, market risk and prepayment and extension risk, as well as the risk of default on the underlying asset. In addition, investments in CLOs carry additional risks, including, but not limited to: (i) the possibility that distributions from collateral securities will not be adequate to make interest or other payments; (ii) the quality of the collateral may decline in value or default; (iii) risks related to the capability of the servicer of the securitized assets; (iv) the risk that the Portfolio may invest in tranches of CLOs that are subordinate to other tranches; (v) the structure and complexity of the transaction and the legal documents may not be fully understood at the time of investment and could lead to disputes with the issuer or among investors regarding the characterization of proceeds or unexpected investment results; and (vi) the CLO's manager may perform poorly

Please see “Description of Principal Risks” for more information regarding the risks associated with investing in the Portfolio. An investment in the Portfolio is not a bank deposit and is not insured or guaranteed by the Federal Deposit Insurance Corporation or any other government agency.

Performance Information

The performance information shows summary performance information for the Portfolio in a bar chart and an Average Annual Total Returns table. The information provides some indication of the risks of investing in the Portfolio by showing changes in its performance from year to year and by showing how the Portfolio’s average annual total returns compare with the returns of certain indexes. Absent any applicable fee waivers and/or expense limitations, performance would have been lower. The information in the bar chart and Average Annual Total Returns Table does not reflect payment of any applicable “wrap” fees by clients of “wrap-fee” programs that invest in the Portfolio to the program sponsors. The Portfolio’s past performance, before and after taxes, is not necessarily an indication of how the Portfolio will perform in the future.

In addition to the Portfolio’s performance, the Average Annual Total Returns table includes performance of: (i) a broad-based securities market index (i.e., a regulatory index) and (ii) two supplemental indexes. It is not possible to invest directly in an unmanaged index. The Portfolio’s regulatory index is the Bloomberg U.S. Aggregate Index. The Portfolio’s regulatory index is shown in connection with certain regulatory requirements to provide a broad measure of market performance. The Bloomberg U.S. Aggregate Index represents securities that are SEC-registered, taxable, and dollar denominated. The index covers the U.S. investment grade fixed rate bond market, with index components for government and corporate securities, mortgage pass-through securities, and asset-backed securities. These major sectors are subdivided into more specific indices that are calculated and reported on a regular basis. The Bloomberg U.S. TIPS Index is a supplemental index of the Portfolio. The ICE BofA U.S. Treasury Inflation-Linked 7-10 Year Index is also a supplemental index of the Portfolio.

Calendar Year Total Returns

Best Quarter	June 30, 2020	7.16%
Worst Quarter	June 30, 2022	-9.44%

Average Annual Total Returns (for periods ended 12/31/25)

	1 Year	5 Years	10 Years
Fixed Income SHares: Series R - Before Taxes	11.20%	0.78%	3.85%
Fixed Income SHares: Series R - After Taxes on Distributions(1)	9.23%	-1.40%	2.05%
Fixed Income SHares: Series R - After Taxes on Distributions and Sale of Portfolio Shares(1)	6.53%	-0.35%	2.18%
Bloomberg U.S. Aggregate Index (reflects no deductions for fees, expenses or taxes)	7.30%	-0.36%	2.01%
Bloomberg U.S. TIPS Index (reflects no deductions for fees, expenses or taxes)	7.01%	1.12%	3.09%
ICE BofA U.S. Treasury Inflation-Linked 7-10 Year Index (reflects no deductions for fees, expenses or taxes)	8.90%	0.73%	3.11%

After-tax returns are calculated using the highest historical individual federal marginal income tax rates and do not reflect the impact of state and local taxes. Actual after-tax returns depend on an investor's tax situation and may differ from tax returns shown. After-tax returns are not relevant to investors who hold their shares through tax advantaged arrangements such as 401(k) plans or individual retirement accounts. In some cases the return after taxes may exceed the return before taxes due to an assumed tax benefit from any losses on a sale of Portfolio shares at the end of the measurement period.

Investment Adviser/Portfolio Managers

PIMCO serves as the investment adviser and administrator for the Portfolio. The Portfolio is jointly and primarily managed by Mike Cudzil and Daniel He. Mr. Cudzil is a Managing Director and portfolio manager in PIMCO’s Newport Beach office. Mr. He is an Executive Vice President and portfolio manager in PIMCO’s Newport Beach office. Mr. Cudzil has managed the Portfolio since June 2025. Mr. He has managed the Portfolio since December 2019.

Purchase and Sale of Portfolio Shares

Shares of the Portfolio may be purchased only by or on behalf of “wrap” account clients where PIMCO or Virtus Fund Advisers, LLC (each, as applicable, the “Wrap Program Adviser”) has an agreement to serve as

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Summary Prospectus

investment adviser or sub-adviser to the account with the wrap program sponsor (typically a registered investment adviser, bank or broker-dealer) or directly with the client. A client agreement to open an account typically may be obtained by contacting the wrap program sponsor. Minimum investment amounts for investing in a Portfolio can be found in the wrap-fee brochure provided to you by the wrap program sponsor or your investment adviser. Generally, purchase and redemption orders for Portfolio shares are processed at the net asset value (“NAV”) next calculated after the broker-dealer who executes trades for the applicable wrap account receives the order on behalf of the account. Orders received by the broker-dealer prior to the time the Portfolio’s NAV is determined on a business day will be processed at that day’s NAV, even if the order is received by the transfer agent after the Portfolio’s NAV has been calculated that day, as long as the order is received by the transfer agent prior to such time as agreed upon by the transfer agent and the broker-dealer.

Tax Information

The Portfolio’s distributions are generally taxable to you as ordinary income, capital gains or a combination of the two, unless you are investing through a tax-advantaged arrangement, such as a 401(k) plan or an individual retirement account, in which case distributions may be taxable upon withdrawal.

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