An image sensor is provided. The image sensor includes a pixel array including first and second pixels, the first and second pixels receiving the same transfer gate signal and outputting first and second signal voltages, respectively, a transfer gate driver receiving first and second voltages and generating the transfer gate signal, the transfer gate signal having the first voltage as its maximum voltage and having the second voltage as its minimum voltage and a compensation module detecting a variation in the second voltage, generating a compensation voltage based on the variation in the second voltage, and performing a compensation operation.