Company: PTY
Filing Date: 2025-06-06
Form Type: 424B5
Source: 0001193125-25-137029
Chunk: 15

Company: PIMCO CORPORATE & INCOME OPPORTUNITY FUND
Filing Date: 2025-06-06
Form: 424B5
Chunk 15
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 Prospectus Supplement and the accompanying Prospectus omit certain of the information contained in the Registration Statement, and reference is hereby made to the Registration Statement and related exhibits for further information with respect to the Fund and the Common Shares offered hereby. Any statements contained herein concerning the provisions of any document are not necessarily complete, and, in each instance, reference is made to the copy of such document filed as an exhibit to the Registration Statement or otherwise filed with the SEC. Each such statement is qualified in its entirety by such reference. The complete Registration Statement may be obtained from the SEC upon payment of the fee prescribed by its rules and regulations or free of charge through the SEC’s website (http://www.sec.gov). June 6, 2025 | Supplement S-9

Closed-End Funds Base Prospectus September 28, 2023 PIMCO Corporate & Income Opportunity Fund

|                                           | Common Shares |
| PIMCO Corporate & Income Opportunity Fund | PTY           |

Neither the U.S. Securities and Exchange Commission nor the U.S. Commodity Futures Trading Commission has approved or disapproved of these securities or determined that this prospectus is truthful or complete. Any representation to the contrary is a criminal offense. PIMCO Corporate & Income Opportunity Fund (the “Fund”) is a diversified, closed-end management investment company that commenced operations on December 27, 2002, following the initial public offering of its common shares of beneficial interest, par value $0.00001 per share (the “Common Shares”). Investment Objective. The Fund’s investment objective is to seek maximum total return through a combination of current income and capital appreciation. Investment Strategy. The Fund seeks to achieve its investment objective by utilizing a dynamic asset allocation strategy that focuses on duration management, credit quality analysis, risk management techniques and broad diversification among issuers, industries and sectors. The Fund normally invests in a portfolio that consists primarily of corporate debt obligations of varying maturities, other corporate income-producing securities, and income-producing securities of non-corporate issuers. In managing the Fund, Pacific Investment Management Company LLC, the Fund’s investment manager (“PIMCO” or the “Investment Manager”) employs an active approach to allocation among multiple fixed income sectors based on, among other things, market conditions, valuation assessments and economic outlook, credit market trends and other economic factors. The Fund focuses on seeking income generating investment ideas across multiple fixed income sectors, with an emphasis on seeking opportunities in developed and emerging global credit markets. The Common Shares are listed on the New