Provided are an image processing apparatus and an electronic endoscope system that can acquire an observation image that is natural overall and has excellent visibility, while highlighting characteristic parts such as affected parts and parts that are to be examined. A normal observation image captured using normal light and a narrow-band observation image captured using narrow-band light that has a bandwidth narrower than that of normal light are input to the observation image input unit. A characteristic part extraction unit extracts a characteristic part that is included in a narrow-band observation image. A highlight display unit displays a single image in which a part of the normal observation image, the part corresponding to a characteristic part that is included in the narrow-band observation image, is highlighted using the characteristic part.
