Fungal infections were histologically confirmed in 20 stranded sea turtles, including 18 Kemp's ridley turtles (Lepidochelys kempii), 1 green turtle (Chelonia mydas), and 1 leatherback turtle (Dermochelys coriacea). Infection was detected antemortem in six cases. Gross external findings in live turtles included carapace lesions (n = 3) and dermatitis (n = 1). Radiographs revealed evidence of pneumonia in 18 animals. Bronchoscopy detected excessive fluid, mucus, clotted blood, or caseous material within the bronchi and lungs of three turtles. At necropsy, the most common gross lesions were pulmonary granulomas, consolidation, and/or hemorrhage (n = 18), and the most common histologic lesion was severe heterophilic-to-granulomatous pneumonia (n = 18). Nine animals had fungal infection at sites outside of the lung. The most commonly identified genera were Purpureocillium, Beauveria, and Fusarium. Other isolates included Metarhizium sp., Trichoderma sp., Clavispora lusitaniae (Candida lusitaniae), Leptospherulina sp., Penicillium chrysogenum, Mucor sp., and Aspergillus section Nigri. Antifungal susceptibility performed for 10 isolates indicated minimum inhibitory concentrations (milligrams per liter) for fluconazole ranging from 8 to >64, often >32; itraconazole from 0.06 to 16, often ≤1; voriconazole from 0.06 to 2, often ≤0.5; and terbinafine from 0.06 to >2, often ≤2. These data indicate that fluconazole resistance is common among the fungi that cause infection in sea turtles. Based on susceptibility data, itraconazole, voriconazole, or terbinafine may be appropriate for treatment of such infections, but additional clinical research is needed. Results of this study indicate that fungal infections can be difficult to diagnose antemortem in sea turtles, and more aggressive methods of diagnosis, such as lung biopsy, may be indicated for suspected cases.