A door assembly comprises a stationary frame, a movable frame, and an adjusting assembly. The adjusting assembly comprises an adjusting element detachably connected with the stationary frame and having a rod portion; a fixing element connected with the movable frame and having a cavity for receiving the rod portion; and a cam member disposed adjacent to the cavity and movable between an open position in which the movable frame is movable relative to the stationary frame and a closed position in which the movable frame is fixed relative to the stationary frame. The door assembly can be assembled without drilling, minimizing risk of damage to the frames, and can be assembled by a single person.