A mask assembly includes a frame and a mask supported by the frame. The mask includes a plurality of deposition patterns. Each of the plurality of deposition patterns includes a first pattern portion disposed in an active area corresponding to a display area of a display substrate, a second pattern portion disposed in a dummy area corresponding to a non-display area of the display substrate, and a third pattern portion disposed in a dummy outer area also corresponding to the non-display area of the display substrate. The dummy area extends from the active area to the dummy outer area and the dummy outer area extends from the dummy area to an edge of each of the plurality of deposition patterns. The first pattern portion includes a plurality of first holes, the second pattern portion includes a plurality of second holes, and the third pattern portion includes a plurality of grooves.