The demand for pet food is increasing at a robust pace due to the gaining momentum and increasing pet population. The rising cost of commercial pet food has become a matter of concern. Therefore it is the need of hour to develop cost effective along with quality nutritive pet food, which can be achieved by utilization of various animal by-products. It has been proclaimed that slaughter house by-products are traditionally being fed to animals and pets. Various by-products have been attempted in different type of pet foods and feeding other animals besides pet dogs, since these by-products are rich in protein, fats, vitamins and minerals. Therefore this review reflects the use of various processed by-products in pet food products with respect to their nutritive and functional properties.