X0306 4/A 2021-02-16 2021-02-18 0 0001333274 MERCER INTERNATIONAL INC. MERC 0001331804 Heine Eric Xavier SUITE 1120 - 700 WEST PENDER STREET VANCOUVER A1 V6C 1G8 BRITISH COLUMBIA, CANADA 0 1 0 0 VP,Sales,Marketing&Logistics Common Stock 2021-02-16 4 M 0 3911 0 A 69724 D Common Stock 2021-02-16 4 F 0 1956 13.65 D 67768 D Represents the conversion of vested performance share units ("PSUs"). Represents the average of the intraday high and low trading price on February 16, 2021. The Amount of Securities Beneficially Owned Following Reported Transaction(s) is being amended and is not the result of a new transaction. /s/ Eric X. Heine 2021-12-23