An organic light emitting display and a driving method thereof, which can effectively detect degradation information of pixels in a display. An organic light emitting display includes a pixel unit and a degradation detector. The pixel unit has a plurality of pixels positioned at intersection portions of scan lines and data lines. The degradation detector divides the pixel unit into a plurality of first blocks each including a plurality of pixels, and detects degradation information for each second block including a plurality of first blocks. In the degradation detector, the second blocks are divided so that each second block shares one or more first blocks with another second block adjacent thereto.