Nocardia spp. are known as causes of bovine mastitis, pneumonia, cutaneous or subcutaneous abscesses and disseminated disease. Pulmonary infection by Nocardia spp. was diagnosed in a sheep. Grossly, the animal had multiple white, firm, and small nodules in the lung. Microscopically, the nodules consisted of foci of pyogranulomatous inflammation with the presence of macrophages, multinucleated (langhans- type) giant cells and eosinophilic amorphous material with rosette-shape configurations (Splendore-Hoeppli reaction). Tissue samples of the lung were streaked onto bovine blood agar, incubated at 37 oC for 48-72 hours under aerobic condition, and stained with Gram and modified Zeihl-Neelsen staining. Bacteriological investigations confirmed numerous thin, gram-positive, beaded, branching, filamentous and nonacid fast organisms. Finally, on the basis of characteristic gross, histopathological and bacteriological findings pulmonary nocardiosis was diagnosed, and this is the first reported case of pulmonary nocardiosis in a sheep in Iran.