A unit pixel of an image sensor includes a photoelectric conversion unit, a mode control unit, a first signal generation unit and a second signal generation unit. The photoelectric conversion unit generates photo-charges in response to incident light and provides the photo-charges to a first node. The mode control unit prevents the photo-charges from being discharged from the first node in a first operation mode, and generates a sensing current by discharging the photo-charges and generates a sensing voltage proportional to the sensing current in a second operation mode. The first signal generation unit generates an analog signal based on an amount of the photo-charges accumulated in the first node in the first operation mode. The second signal generation unit generates an on signal and an off signal based on a change of the sensing voltage in the second operation mode. The unit pixel provides various sensing outputs effectively.