A 70-year-old woman was admitted to our hospital for the evaluation of a pulmonary nodule in the left S5 segment. On 18F-fluorodeoxyglucose positron emission tomography (18FDG-PET), the nodule showed substantial uptake of 18F-fluorodeoxyglucose. Bronchoscopy was performed, but the cytology was negative. For a pathological diagnosis, a lung biopsy was carried out using video-associated thoracoscopy. The biopsy specimen showed granuloma formation with multinuclear giant cells. An acid-fast bacteria culture of the specimen was positive for Mycobacterium intracellulare. An atypical mycobacterium infection should be considered as a possibility when the 18FDG-PET of patients with pulmonary nodules is interpreted.