This review is a general discussion of common zoonotic infections of companion animals in the United States. Microbes, routes of transmission, and risks to immunocompromised persons are discussed. The primary focus of this article is dogs and cats, although zoonoses of avian, rodent, and rabbit companion animals are discussed in brief. An awareness of zoonoses will allow veterinarians and physicians to collaboratively prevent transmission and treat clinical disease in both human and veterinary patients.