Iron Mountain Incorporated
US ˙ NYSE ˙ US46284V1017

SecurityIRM / Iron Mountain Incorporated
InstitutionPacer Advisors, Inc.
Latest Disclosed Ownership167,170 shares
Latest Disclosed Value $ 17,074,744
Pacer Advisors, Inc. reports 25.16% decrease in ownership of IRM / Iron Mountain Incorporated

On May 6, 2026 - Pacer Advisors, Inc. filed a 13F-HR form disclosing ownership of 167,170 shares of Iron Mountain Incorporated (US:IRM) valued at $17,074,744 USD as of March 31, 2026. The entity filed a previous 13F-HR/A on February 24, 2026 disclosing 223,367 shares of Iron Mountain Incorporated. This represents a change in shares of -25.16% during the quarter. The current value of the position is $21,389,402 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)
2026-05-06 2026-03-31 13F Iron Mountain REIT - Domestic 46284V101 167,170 -56,197 -25.16 17,075 -7.85 0.0440
2026-02-24 2025-12-31 13F/A-1 Iron Mountain REIT - Domestic 46284V101 223,367 -7,868 -3.40 18,528 -21.40 0.0473
2026-02-04 2025-12-31 13F Iron Mountain REIT - Domestic 46284V101 223,367 -7,868 18,528 0.0253
2025-10-15 2025-09-30 13F Iron Mountain REIT - Domestic 46284V101 231,235 10,952 4.97 23,572 4.33 0.0594
2025-08-12 2025-06-30 13F Iron Mountain REIT - Domestic 46284V101 220,283 -24,203 -9.90 22,594 7.41 0.0562
2025-05-06 2025-03-31 13F Iron Mountain REIT - Domestic 46284V101 244,486 32,942 15.57 21,036 -5.40 0.0492
2025-01-22 2024-12-31 13F Iron Mountain REIT - Domestic 46284V101 211,544 13,437 6.78 22,235 -5.55 0.0480
2024-11-12 2024-09-30 13F Iron Mountain REIT - Domestic 46284V101 198,107 -43,554 -18.02 23,541 8.70 0.0498
2024-08-13 2024-06-30 13F Iron Mountain REIT - Domestic 46284V101 241,661 -51,252 -17.50 21,658 -7.82 0.0491
2024-05-10 2024-03-31 13F Iron Mountain REIT - Domestic 46284V101 292,913 -87,113 -22.92 23,495 -11.66 0.0540
2024-01-16 2023-12-31 13F IRON MTN INC DEL REIT - Domestic 46284V101 380,026 -27,651 -6.78 26,594 9.73 0.0753
2023-11-13 2023-09-30 13F IRON MTN INC DEL REIT - Domestic 46284V101 407,677 -86,072 -17.43 24,236 -13.61 0.0928
2023-07-12 2023-06-30 13F IRON MTN INC DEL REIT - Domestic 46284V101 493,749 -156,402 -24.06 28,055 -18.45 0.1129
2023-05-02 2023-03-31 13F IRON MTN INC DEL REIT - Domestic 46284V101 650,151 -87,319 -11.84 34,399 -6.43 0.1470
2023-02-06 2022-12-31 13F IRON MTN INC DEL REIT - Domestic 46284V101 737,470 -250,664 -25.37 36,763 -15.39 0.1881
2022-10-18 2022-09-30 13F IRON MTN INC DEL REIT - Domestic 46284V101 988,134 -35,657 -3.48 43,448 -12.84 0.3027
2022-08-12 2022-06-30 13F IRON MTN INC REIT - Domestic 46284V101 1,023,791 -190,426 -15.68 49,848 -25.91 0.3702
2022-04-05 2022-03-31 13F IRON MTN INC REIT - Domestic 46284V101 1,214,217 -328,091 -21.27 67,280 -16.64 0.5515
2022-02-03 2021-12-31 13F IRON MTN INC REIT - Domestic 46284V101 1,542,308 -10,542 -0.68 80,709 19.62 0.8278
2021-10-15 2021-09-30 13F IRON MTN INC REIT - Domestic 46284V101 1,552,850 365,854 30.82 67,471 34.31 0.8520
2021-07-21 2021-06-30 13F IRON MTN INC REIT - Domestic 46284V101 1,186,996 -122,976 -9.39 50,234 3.61 0.7190
2021-04-05 2021-03-31 13F IRON MTN INC REIT 46284V101 1,309,972 -437,245 -25.03 48,482 -5.87 0.8426
2021-01-20 2020-12-31 13F IRON MTN INC REIT 46284V101 1,747,217 382,096 27.99 51,508 40.84 0.9673
2020-10-19 2020-09-30 13F IRON MTN INC REIT 46284V101 1,365,121 108,085 8.60 36,572 11.47 0.7779
2020-07-29 2020-06-30 13F IRON MTN INC REIT 46284V101 1,257,036 535,401 74.19 32,809 81.93 0.6643
2020-04-23 2020-03-31 13F IRON MTN INC REIT 46284V101 721,635 459,252 175.03 18,034 115.67 0.3629
2020-02-10 2019-12-31 13F IRON MTN INC REIT 46284V101 262,383 64,078 32.31 8,362 30.19 0.3778
2019-10-10 2019-09-30 13F IRON MTN INC REIT 46284V101 198,305 108,279 120.28 6,423 127.93 0.1444
2019-08-12 2019-06-30 13F IRON MTN INC REIT 46284V101 90,026 42,563 89.68 2,818 67.34 0.0689
2019-04-10 2019-03-31 13F IRON MTN INC REIT 46284V101 47,463 39,018 462.02 1,684 514.60 0.0467
2019-02-13 2018-12-31 13F IRON MTN INC REIT 46284V101 8,445 -9,269 -52.33 274 -55.16 0.0097
2018-11-14 2018-09-30 13F IRON MTN INC REIT 46284V101 17,714 1,764 11.06 611 9.50 0.0230
2018-08-14 2018-06-30 13F IRON MTN INC REIT 46284V101 15,950 5,634 54.61 558 64.60 0.0253
2018-05-14 2018-03-31 13F Iron Mountain REIT 46284V101 10,316 1,782 20.88 339 5.28 0.0187
2018-02-14 2017-12-31 13F Iron Mountain Com 46284V101 8,534 4,105 92.68 322 87.21 0.0226
2017-11-08 2017-09-30 13F Iron Mountain Com 46284V101 4,429 444 11.14 172 25.55 0.0152
2017-08-08 2017-06-30 13F IRON MTN INC Com 46284V101 3,985 322 8.79 137 4.58 0.0135
2017-05-09 2017-03-31 13F IRON MTN INC Com 46284V101 3,663 121 3.42 131 13.91 0.0161
2017-02-08 2016-12-31 13F IRON MTN INC Com 46284V101 3,542 -22 -0.62 115 -14.18 0.0164
2016-11-10 2016-09-30 13F IRON MTN INC Com 46284V101 3,564 -16,122 -81.90 134 -82.91 0.0204
2016-08-12 2016-06-30 13F IRON MTN INC Com 46284V101 19,686 17,197 690.92 784 833.33 0.1238
2016-05-13 2016-03-31 13F IRON MTN INC Com 46284V101 2,489 -327 -11.61 84 10.53 0.0191
2016-02-17 2015-12-31 13F IRON MTN INC Com 46284V101 2,816 2,816 76 0.0179
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.