UNITED STATES

SECURITIES AND EXCHANGE COMMISSION

WASHINGTON, DC 20549

FORM 8-K

CURRENT REPORT

PURSUANT TO SECTION 13 OR 15(D)

OF THE SECURITIES EXCHANGE ACT OF 1934

Date of report (Date of earliest event reported) ~~May 16~~June 23, ~~2025~~ 2026

PIMCO Corporate & Income Opportunity Fund

Fund

(Exact Name of Registrant as Specified in Its Charter)

Massachusetts


Massachusetts	811-21238	46-6121513
(State or other jurisdiction of incorporation)	(Commission File Number)	(IRS Employer Identification No.)

(State or Other Jurisdiction of Incorporation)

1633 Broadway

New York, NY

10019

(Address of principal executive offices)

(Zip Code)

811-21238		46-6121513
(Commission File Number)		(IRS Employer Identification No.)
1633 Broadway, New York, NY		10019
(Address of Principal Executive Offices)		(Zip Code)

(844) 337-4626

(~~844)~~Registrant’s ~~877-4626~~telephone number, including area code)

(Registrant’s Telephone Number, Including Area Code)

Not Applicable

(Former Name or Former Address, if Changed Since Last Report)

Check the appropriate box below if the Form 8-K filing is intended to simultaneously satisfy the filing obligation of the registrant under any of the following provisions:

☐ Written communications pursuant to Rule 425 under the Securities Act (17 CFR 230.425)

☐ Soliciting material pursuant to Rule 14a-12 under the Exchange Act (17 CFR 240.14a-12)

☐ Pre-commencement communications pursuant to Rule 14d-2(b) under the Exchange Act (17 CFR 240.14d-2(b))

☐ Pre-commencement communications pursuant to Rule 13e-4(c) under the Exchange Act (17 CFR 240.13e-4(c))

Securities registered pursuant to Section 12(b) of the Act:

Title of each class ~~Trading Symbol~~TradingSymbol(s) Name of each ~~exchange~~exchangeon on which registered Common shares PTY New York Stock Exchange

Indicate by check mark whether the registrant is an emerging growth company as defined in Rule 405 of the Securities Act of 1933 (§230.405 of this chapter) or Rule 12b-2 of the Securities Exchange Act of 1934 (§240.12b-2 of this chapter).

Emerging growth company ☐

If an emerging growth company, indicate by check mark if the registrant has elected not to use the extended transition period for complying with any new or revised financial accounting standards provided pursuant to Section 13(a) of the Exchange Act. ☐

Item 8.01 Other Events.

On ~~May~~June 1523, ~~2025~~2026, ~~PIMCO~~the ~~Corporate &~~Board ~~Income~~of ~~Opportunity~~Trustees approved a change to the Fund’s ~~(NYSE:~~80% ~~PTY)~~investment (policy. Effective August 28, 2026, the “Fund”) ~~posted~~invests, anunder ~~amended~~normal ~~and~~circumstances, ~~restated~~at ~~Section 19 Notice~~least to80% of its ~~website~~net atassets ~~www.pimco.com~~(plus ~~that~~the ~~sets~~amount ~~forth~~of anany ~~estimate~~borrowings for investment purposes) in corporate debt obligations of ~~the~~varying ~~sources~~maturities and/or income-producing investments, which may include those of non-corporate issuers. The supplement to the Fund’s ~~distribution~~prospectus ~~payable~~and ~~May 1,~~statement ~~2025~~of toadditional ~~shareholders~~information ofdisclosing ~~record~~this onchange ~~April 11,~~is ~~2025~~attached hereto as Exhibit 99.1.

~~SIGNATURE~~Item 9.01 Financial Statements and Exhibits.

Pursuant to the requirements of the Securities Exchange Act of 1934, the Registrant has duly caused this report to be signed on its behalf by the undersigned hereunto duly authorized.


(d)		Exhibits

99.1		Supplement, dated June 24, 2026

104		Cover Page Interactive Data File (embedded within the Inline XBRL document)

~~PIMCO~~SIGNATURE ~~Corporate & Income Opportunity Fund By: /s/ Joshua D. Ratner Name: Joshua D. Ratner Title: President~~

~~Date:~~Pursuant ~~May 16~~to the requirements of the Securities Exchange Act of 1934, ~~2025~~the Registrant has duly caused this report to be signed on its behalf by the undersigned hereunto duly authorized.


PIMCO Corporate & Income Opportunity Fund

By:		/s/ Ryan G. Leshaw
Name:		Ryan G. Leshaw
Title:		Chief Legal Officer and Secretary

Date: June 24, 2026

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