Iron Mountain IRM Institutional Ownership

Ownership Summary

Iron Mountain Inc (NYSE:IRM) showed up in the 13F filings of 1,064 institutional investors as of March 2026.

• They owned 84.7% of outstanding stock in March 2026, down from 87.7% the prior quarter.
• They increased total shares held in Iron Mountain by 22.96% from the prior quarter, while the number of investors in IRM increased 7.58% year over year.
• During the quarter, 575 of these 1,064 funds increased positions in IRM, 339 reduced exposure, and 150 held steady.
• The aggregate institutional position in Iron Mountain amounted to 251.3Mn shares as of March 2026, up by 46.93Mn shares quarter on quarter, and down 7.62Mn shares year over year.
• BlackRock, Inc. holds the largest position in IRM at 33.02Mn shares as of March 31, 2026, or 11.12% of shares outstanding.
• Leading buyers of Iron Mountain shares for the quarter ending March 2026 were VANGUARD PORTFOLIO MANAGEMENT LLC (25.02Mn), VANGUARD CAPITAL MANAGEMENT LLC (18.76Mn), VANGUARD FIDUCIARY TRUST CO (1.65Mn), Morgan Stanley (1.05Mn), AQR CAPITAL MANAGEMENT LLC (922.88K).
• The largest sales of IRM for the quarter ending March 2026 came from Cohen & Steers, Inc. (2.73Mn), Pictet Asset Management Holding SA (1.43Mn), Contour Asset Management LLC (1.39Mn), HSBC HOLDINGS PLC (838.7K), Goldman Sachs Group Inc (833.13K).
• Business Quant data shows the 10 biggest positions in Iron Mountain as of March 2026 are held by BlackRock, Inc. (33.02Mn), VANGUARD PORTFOLIO MANAGEMENT LLC (25.02Mn), VANGUARD CAPITAL MANAGEMENT LLC (18.76Mn), State Street Corp (17.55Mn), Cohen & Steers, Inc. (16.17Mn), GEODE CAPITAL MANAGEMENT, LLC (8.49Mn), FMR LLC (7.48Mn), Morgan Stanley (4.65Mn), Principal Financial Group Inc (4.57Mn), DIMENSIONAL FUND ADVISORS LP (4.55Mn).