An organic light emitting display device includes a display panel including a plurality of pixels, wherein each pixel includes a driving transistor outputting a data current based on a data voltage to emit light from an organic light emitting diode; and a panel driver which drives the display panel in a sensing mode and a display mode, wherein the panel driver calculates a threshold voltage prediction value of the driving transistor for each pixel by sensing a mobility and a threshold voltage of the driving transistor for each pixel through a reference line connected with a sensing node between the driving transistor and the organic light emitting diode of each pixel for the sensing mode, and the panel driver drives each pixel based on the threshold voltage prediction value of the driving transistor of each pixel for the display mode.