Provided are an image sensor and an imaging device including the same. The image sensor is configured to generate illuminance data by receiving a light signal including image information of an object and ambient light information and includes a sensing module including a pixel array including a plurality of unit pixels, configured to sense the light signal irradiated to the pixel array and to generate pixel data corresponding to the sensed light signal, and an illuminance data generator configured to generate illuminance data corresponding to ambient light based on the pixel data, wherein the illuminance data generator is configured to generate the illuminance data based on pixel data when the light signal is not focused on the pixel array.