With the development of the pet industry, public attention to pet food safety and nutritional health has been continuously increasing. Postbiotics were initially defined as inactivated microorganisms or microbial cellular components that confer health benefits to the host. Compared with probiotics, postbiotics possess superior safety and stability. They can effectively eliminate the potential risk of horizontal transfer of drug-resistant genes carried by live bacteria, and also feature better manufacturability and storage performance. At present, most research on postbiotics has focused on humans and large domestic animals, with relatively few applications in dogs and cats. This indicates that further research on postbiotics in canines and felines is still needed to better promote their practical application in promoting pet food health. This article provides a comprehensive review of the current research status of postbiotics, focusing on their potential benefits and mechanisms for pet health. It proposes that future studies should concentrate on in vivo experimental validation to clarify the safety, optimal dosage, and specific functions of postbiotics in companion animals. Such research will offer a scientific basis for the application of postbiotics in pet food formulations, ultimately promoting the health and welfare of pets.