Nocardiosis is a rare disease generally caused by members of Nocardia asteroides complex, particularly in immunosupressed patients. Nocardia cyriacigeorgica is a newly described member of this complex. In this article, a case of pulmonary nocardiosis with a large solitary cavitary nodule caused by N. cyriacigeorgica, in a patient receiving corticosteroid therapy was presented. A 29 years old male patient receiving prednisolone for 5 months was admitted to our hospital with fever, cough, right thoracic pain and night sweats. Computed tomography scan of chest demonstrated a large solitary cavitary nodule in the right lower lobe. Gram stained smear of the sputum revealed gram-positive, beaded, branched filamentous bacilli. On the third day of his admission, a catalase positive, oxidase negative and immotile bacilli, compatible with Nocardia spp., were isolated from the sputum sample taken at the day of admission. The isolated bacterium was identified as N. cyriacigeorgica by reference laboratory (Lyon, France). Oral trimethoprim (320 mg/day) and sulfamethoxazole (1600 mg/day) therapy given for three months, resulted in complete cure of the lesion without any sequela. This was the fourth case of pulmonary nocardiosis caused by N. cyriacigeorgica reported from Turkey. Microbiological examination of sputum is the most important tool for the diagnosis. Treatment with appropriate antibiotics may achieve complete cure even in large cavitary lesions. In conclusion, pulmonary nocardiosis should be considered in differential diagnosis of solitary cavitary nodules, especially in immunocompromised patients.