It is an object to provide an animal weight estimation system, an animal weight estimation method, and a program, for suppressing increase of cost and improving safety when measuring a weight of an animal. An animal weight estimation system 1 for estimating a weight of an animal captures the animal, acquires outline data or a feature amount of the animal from a captured image which is captured, measures a distance between the animal and an image capturing position of the animal and estimates a weight of the animal from the acquired outline data and the measured distance when the outline data are acquired, and estimates the weight of the animal form the acquired feature amount when the feature amount is acquired.