An image sensor includes a pixel array including a pixel array comprising a first pixel and a second pixel which are electrically connected to a first column line, a row driver configured to receive a clamp voltage and a selection voltage, select the first pixel based on the clamp voltage and select the second pixel based on the selection voltage. A voltage of the first column line is determined based on a higher voltage among a first output voltage of the first pixel and a second output voltage of the second pixel during a read operation of the second pixel.