A luminance control circuit of a display device includes a target luminance gain calculator calculating a target luminance gain based on an average luminance of a first image signal when the first image signal is determined to be a still image, an output luminance gain calculator calculating an output luminance gain based on a previous output luminance gain of a previous frame and the target luminance gain of a present frame, and a luminance scaler outputting a second image signal obtained by changing a luminance of the first image signal based on the output luminance gain.