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    <dei:DocumentsIncorporatedByReferenceTextBlock contextRef="P10_01_2024To09_30_2025" id="ixv-212">Documents Incorporated by Reference: Portions of the Registrant&#x2019;s Proxy Statement relating to the Registrant&#x2019;s 2026 Annual Meeting of Stockholders to be filed not later than 120 days after the end of the fiscal year covered by this Annual Report on Form &lt;div style="white-space: nowrap; letter-spacing: 0px; top: 0px;display:inline;"&gt;10-K&lt;/div&gt; are incorporated by reference into Part III of this Report.</dei:DocumentsIncorporatedByReferenceTextBlock>
    <dei:AmendmentDescription contextRef="P10_01_2024To09_30_2025" id="ixv-223">PennantPark Investment Corporation, a Maryland corporation, or together with its subsidiaries, where applicable, or the Company, which may also be referred to as &#x201c;we,&#x201d; &#x201c;us&#x201d; or &#x201c;our,&#x201d; is filing this Amendment No.&#160;2, or this Amendment, to our Annual Report on Form 10-K for the fiscal year ended September 30, 2025, or the Form 10-K, which was initially filed with the Securities and Exchange Commission, or the SEC, on November&#160;24, 2025. We are filing this Amendment to provide audited consolidated financial statements for our investment in an unconsolidated portfolio company, AKW Holdings Limited (&#x201c;AKW&#x201d;), as of December 31, 2025 and for the year ended December 31, 2025 and unaudited consolidated financial statements for our investment in AKW as of December&#160;31, 2024 and for each of the years in the two-year period ended December&#160;31, 2024 (as Exhibit 99.5). We have determined that this unconsolidated portfolio company has met the conditions of a significant subsidiary under Rule 1-02(w) of Regulation S-X for which we are required, pursuant to Rule 3-09 of Regulation S-X, to provide separate financial statements as exhibits to the Form 10-K. In accordance with Rule 3-09(b)(1), the separate audited and unaudited consolidated financial statements of AKW are being filed as an amendment to the Form 10-K. This Amendment also includes the filing of new Exhibits 31.1, 31.2, 32.1 and 32.2, certifications of our Chief Executive Officer and Chief Financial Officer, pursuant to Rule 13a-14(a) and (b)&#160;of the Securities Exchange Act of 1934, as amended. Except as described above, no other changes have been made to the Form 10-K. This Amendment does not reflect subsequent events that may have occurred after the original filing date of the Form 10-K or modify or update in any way disclosures made in the Form 10-K, except as required to reflect the revisions discussed above. Among other things, forward-looking statements made in the Form 10-K have not been revised to reflect events that occurred or facts that became known to us after filing of the Form 10-K, and such forward-looking statements should be read in their historical context. Furthermore, this Amendment should be read in conjunction with the Form 10-K and with our subsequent filings with the SEC. </dei:AmendmentDescription>
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