X0306 4 2015-09-08 0 0001020569 IRON MOUNTAIN INC IRM 0001595956 Tomovcsik John C/O IRON MOUNTAIN INCORPORATED ONE FEDERAL STREET BOSTON MA 02110 0 1 0 0 EVP, G. Mgr., Rec. & Inf. Mgmt Common Stock, par value $.01 per share 2015-09-08 4 M 0 3650 0 A 29511 D Common Stock, par value $.01 per share 2015-09-08 4 F 0 1112 28.58 D 28399 D Restricted Stock Units 2015-09-08 4 M 0 3650 0 D Common Stock 3650 0 D This acquisition is reported to reflect the partial vesting of restricted stock units ("RSUs") previously granted to the Reporting Person on September 8, 2011. Includes 648 shares acquired under the Iron Mountain Incorporated Employee Stock Purchase Plan since the last Section 16 filing by the Reporting Person. Each RSU represents a contingent right to receive one share of Iron Mountain Incorporated common stock ("Common Stock"). The RSUs, representing a contingent right to receive a total of 13,774 shares of Common Stock, were granted to the Reporting Person on September 8, 2011 and have vested in four substantially equal annual installments, the last of which was on September 8, 2015. The number of RSUs granted includes previously reported RSUs allocated on November 4, 2014 in connection with the special distribution declared by the Board of Directors of Iron Mountain Incorporated on September 15, 2014 and paid on November 4, 2014. /s/ Ernest W. Cloutier, under Power of Attorney dated January 9, 2014, from John Tomovcsik 2015-09-09