An organic light emitting diode (OLED) display device includes a display panel including a plurality of pixel rows; a driving circuit configured to: provide a first display data to the plurality of pixel rows in a normal mode; provide a second display data including black data to the plurality of pixel rows in a dimming mode, in response to a mode signal; and decrease a second luminance of the display panel in the dimming mode to a level lower than a first luminance of the display panel in the normal mode; and a power supply configured to apply a lower power supply voltage and a high power supply voltage to the display panel, the power supply providing the mode signal.