A drive device for a movable furniture part has a lockable ejection device for ejecting the movable furniture part from a closed position into an open position. The ejection device can be unlocked by pressing the movable furniture part into an over-pressed position situated behind the closed position in the closing direction. A blocking element is provided which has a blocking position in which the blocking element prevents the unlocking of the ejection device upon reaching the pressed-over position, and which has a release position in which the ejection device can be unlocked upon reaching the pressed-over position.