A deposition mask assembly for manufacturing a plurality of display devices includes a frame having an opening area, a first open mask disposed on the frame and having a first body portion defining a plurality of patterns overlapping the opening area, and a second open mask disposed on the first open mask and having a second body portion defining a plurality of opening portions overlapping the patterns of the first open mask, in which each of the patterns includes an auxiliary pattern spaced apart from the first body portion and a first bridge pattern connecting the first body portion and the auxiliary pattern.