In the southeastern and central areas of the United States, Blastomyces dermatitidis is a well-recognized cause of infection in dogs as well as humans. Despite close contact between humans and infected dogs, no instance of zoonotic transmission of blastomycosis has previously been documented. We report a case of human blastomycosis that resulted from the bite of an infected dog. Physicians practicing in areas where blastomycosis is endemic should consider the diagnosis of inoculation blastomycosis when evaluating patients with dog bite wounds that heal poorly. Likewise, veterinarians should be aware of this potential mode of transmission and exercise appropriate caution when handling dogs suspected of having blastomycosis.