Company: PTY
Filing Date: 2025-06-06
Form Type: 424B5
Source: 0001193125-25-137029
Chunk: 1

Company: PIMCO CORPORATE & INCOME OPPORTUNITY FUND
Filing Date: 2025-06-06
Form: 424B5
Chunk 1
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 related to the prevailing market prices or at negotiated prices. JonesTrading will be entitled to compensation of up to 1.00% of the gross proceeds with respect to sales of the Common Shares actually effected by JonesTrading under the Sales Agreement. In connection with the sale of the Common Shares on our behalf, JonesTrading may be deemed to be an “underwriter” within the meaning of the Securities Act and the compensation of JonesTrading may be deemed to be underwriting commissions or discounts. JonesTrading is not required to sell any specific number or dollar amount of Common Shares, but will use its commercially reasonable efforts to sell the Common Shares offered by this Prospectus Supplement and the accompanying Prospectus. There is no arrangement for Common Shares to be received in an escrow, trust or similar arrangement. You should review the information set forth under “Prospectus Supplement Summary - Risks” on page S-4 of this Prospectus Supplement and “Principal Risks of the Fund” starting on page 58 of the accompanying Prospectus before investing in the Common Shares. Neither the U.S. Securities and Exchange Commission (“SEC”) nor the U.S. Commodity Futures Trading Commission have approved or disapproved of these securities or determined that this Prospectus is truthful or complete. Any representation to the contrary is a criminal offense. Prospectus Supplement dated June 6, 2025

June 6, 2025 | Supplement S-1

You should read this Prospectus Supplement and the accompanying Prospectus and the information incorporated by reference herein and therein before deciding whether to invest in the Common Shares and retain them for future reference. The Prospectus Supplement and the accompanying Prospectus and the information incorporated by reference herein and therein contain important information about the Fund. Material that has been incorporated by reference and other information about us can be obtained from us by calling toll free (844) 33-PIMCO (844-337-4626) or by writing to the Fund at c/o Pacific Investment Management Company LLC, 1633 Broadway, New York, New York 10019. The Fund’s Statement of Additional Information and most recent annual and semiannual reports are available, free of charge, on the Fund’s website (http://www.pimco.com/prospectuses). You can obtain the same information, free of charge, from the SEC’s website (http://www.sec.gov). Table of Contents Prospectus Supplement

| About this Prospectus Supplement                       | S-3 |
| Cautionary Notice Regarding Forward-Looking Statements | S-3