A method of operating a display device may include the following steps: in a first frame period, before turning off a gate initialization transistor, changing an initialization voltage from a first level to a second level and subsequently returning the initialization voltage to the first level; in a second frame period, before turning off the gate initialization transistor, changing the initialization voltage from the first level to the second level and/or a third level and subsequently returning the initialization voltage to the first level. The display device may include the gate initialization transistor and a driving transistor. A first electrode the gate initialization transistor may receive the initialization voltage. A second electrode of the gate initialization transistor may be electrically connected to a gate electrode of the driving transistor. The first level, the second level, and the third level may be unequal to each other.