Iron Mountain Incorporated
US ˙ NYSE ˙ US46284V1017

SecurityIRM / Iron Mountain Incorporated
InstitutionCerity Partners LLC
Latest Disclosed Ownership89,510 shares
Latest Disclosed Value $ 9,142,551
Cerity Partners LLC reports 86.43% increase in ownership of IRM / Iron Mountain Incorporated

On May 15, 2026 - Cerity Partners LLC filed a 13F-HR form disclosing ownership of 89,510 shares of Iron Mountain Incorporated (US:IRM) valued at $9,142,551 USD as of March 31, 2026. The entity filed a previous 13F-HR on February 11, 2026 disclosing 48,012 shares of Iron Mountain Incorporated. This represents a change in shares of 86.43% during the quarter. The current value of the position is $11,452,804 USD.

Institutional Ownership: 13F and NPORT Filings

The Security and Class in the table below are shown exactly as filed by the investor. We do our best to track continuity of investments through acquisitions, and this will be reflected in the table as changes in names. In addition to descriptive data, performance of the investment is shown over time. To calculate quarterly performance, we first calculate cost basis of the shares purchased during the quarter, then use that to calculate gross profit. Quarterly return is Gross Profit / Starting Portfolio value.

Note that cost basis is calculated and stored in thousands, so small quarterly changes in shares frequently result in a cost basis of zero.

Upgrade to unlock premium data and export to Excel .

Disclosed Equity Positions (from 13F/NPORT Filings)
File
Date		 Effective
Date		Form Security Class ID Avg Price
Paid (Est)		 Reported
Shares		 ΔShares ΔShares
(%)		 Reported
Value
(x1000)		 ΔValue
(%)		 Alloc
(%)		 ΔAlloc ΔAlloc (%) Cost Basis
(x1000)		 Unrealized
Gain/Loss
(x1000)
2026-05-15 2026-03-31 13F IRON MTN INC DEL COM 46284V101 89,510 41,498 86.43 9,143 129.58 0.0129
2026-02-11 2025-12-31 13F IRON MTN INC DEL COM 46284V101 48,012 9,825 25.73 3,983 2.31 0.0058
2025-10-22 2025-09-30 13F IRON MTN INC DEL COM 46284V101 38,187 2,895 8.20 3,893 7.54 0.0063
2025-08-13 2025-06-30 13F IRON MTN INC DEL REIT 46284V101 35,292 1,222 3.59 3,620 23.47 0.0065
2025-04-30 2025-03-31 13F IRON MTN INC DEL REIT 46284V101 34,070 1,234 3.76 2,931 -19.12 0.0059
2025-02-13 2024-12-31 13F IRON MTN INC DEL COM 46284V101 32,836 3,474 11.83 3,625 3.87 0.0079
2024-11-12 2024-09-30 13F IRON MTN INC DEL REIT 46284V101 29,362 9,442 47.40 3,489 95.46 0.0077
2024-08-13 2024-06-30 13F IRON MTN INC DEL COM 46284V101 19,920 -2,473 -11.04 1,785 -0.61 0.0047
2024-05-14 2024-03-31 13F IRON MTN INC DEL REIT 46284V101 22,393 11,870 112.80 1,797 143.69 0.0047
2024-01-26 2023-12-31 13F IRON MTN INC DEL REIT 46284V101 10,523 10,523 737 0.0024
2023-11-14 2023-09-30 13F IRON MTN INC DEL REIT 46284V101 0 -11,443 -100.00 0 -100.00
2023-08-14 2023-06-30 13F IRON MTN INC DEL REIT 46284V101 11,443 -191 -1.64 650 5.52 0.0025
2023-05-11 2023-03-31 13F IRON MTN INC DEL COM 46284V101 11,634 1,742 17.61 617 24.95 0.0015
2023-02-15 2022-12-31 13F IRON MTN INC DEL COM 46284V101 9,892 -937 -8.65 493 3.35 0.0032
2022-11-14 2022-09-30 13F IRON MTN INC DEL REIT 46284V101 10,829 -1,092 -9.16 477 -17.90 0.0057
2022-08-10 2022-06-30 13F IRON MTN INC COM 46284V101 11,921 -7,173 -37.57 581 -45.09 0.0064
2022-04-25 2022-03-31 13F IRON MTN INC Stock 46284V101 19,094 -9,091 -32.25 1,058 -28.17 0.0164
2022-02-14 2021-12-31 13F IRON MTN INC Stock 46284V101 28,185 1,793 6.79 1,473 28.42 0.0224
2021-10-25 2021-09-30 13F Iron Mountain US Hol REIT REIT 46284V101 26,392 11 0.04 1,147 2.78 0.0252
2021-08-11 2021-06-30 13F IRON MTN INC REIT 46284V101 26,381 -4,025 -13.24 1,116 -0.80 0.0244
2021-08-11 2021-03-31 13F/A-1 IRON MTN INC REIT 46284V101 30,406 -17,866 -37.01 1,125 -20.94 0.0267
2021-05-12 2021-03-31 13F IRON MTN INC REIT 46284V101 30,380 -17,892 1,124 0.0333
2021-02-11 2020-12-31 13F IRON MTN INC REIT 46284V101 48,272 3,771 8.47 1,423 19.38 0.0456
2020-11-12 2020-09-30 13F IRON MTN INC COM 46284V101 44,501 1,848 4.33 1,192 7.10 0.0490
2020-08-17 2020-06-30 13F/A-1 IRON MTN INC COM 46284V101 42,653 2,232 5.52 1,113 15.70 0.0615
2020-08-14 2020-06-30 13F IRON MTN INC COM 46284V101 42,653 2,232 1,113 61,384.6118
2020-05-14 2020-03-31 13F IRON MTN INC COM 46284V101 40,421 4,343 12.04 962 -16.35 0.0606
2020-02-14 2019-12-31 13F IRON MTN INC COM 46284V101 36,078 36,078 1,150 0.0586
Legend
Shares
The total number of shares held by the institution at the end of the reporting period (the effective date). This is provided in the filing.
Value
The total value of the shares as of the effective date. This is provided in the filing.
Avg. Share Price
The weighted average share price of the shares held by the institution. We use FIFO accounting to determine this price
Class
This is the security class as indicated by the filer. There are a variety of values for this field. Common values include "EC" = equity common, "EP" - equity preferred
Allocation (%)
The percent of the institution's portfolio that this position represents. This is provided in NPORT filings. For 13F filings, we calculate it.
Change in Allocation
The change in allocation from the prior reporting period. This is calculated as current allocation - prior allocation.
Change in Allocation (%)
The percent change in allocation from the prior reporting period. This is calculated as (current allocation - prior allocation) / prior allocation.
Cost Basis
The total cost of the shares held. This is calculated as reported shares * avg. share price
Unrealized Gain/Loss
This is the market value of the position as of the effective date minus the cost basis.