Provided are an endoscope system, a processor device, and an endoscope system operation method capable of adjusting an exposure amount with higher accuracy than in the related art. An endoscope system includes a light source unit that emits illumination light, an image sensor that images an observation target by using the illumination light, an image acquisition unit that acquires plural-color images obtained by imaging the observation target by using the image sensor, and an exposure amount control portion that controls an exposure amount in a case where the image acquisition unit obtains the plural-color images, by using some-color images among the plural-color images.