A stranded bottlenose dolphin (Tursiops truncatus gilli) succumbed to a pulmonary infection of Coccidioides immitis. The dolphin initially presented with mild inspiratory dyspnea that rapidly worsened over 48 hr to include buoyancy abnormalities and finally death. At necropsy, caseous nodules were observed throughout the lungs and perihilar lymph nodes. On histological examination of tissues, double walled organisms containing endospores characteristic of C. immitis were observed in lung, perihilar lymph nodes, and brain. Pyogranulomatous infiltrates were observed in the lung and perihilar lymph nodes only. A DNA Gen-Probe test performed on a purified isolate confirmed infection by C. immitis. Serum was positive for antibodies to C. immitis at a titer of 1:128 and was negative for all known marine morbilliviruses. Although there have been reports of C. immitis infections in free ranging marine wildlife, including California sea lions (Zalophus californianus) and sea otters (Enhydra lutris), this is the first reported case of coccidioidomycosis in a cetacean.