Here, we describe a case of a solitary pulmonary nodule due to Mycobacterium intracellulare infection. To the best of our knowledge, this is the first case reported in Korea. A 45-year- old female, exhibiting no respiratory symptoms, was admitted to our hospital due to the appearance of a solitary pulmonary nodule on a chest radiograph. Computed tomography revealed a 2.5 cm nodule with an irregular shape and some marginal spiculation in the right upper lobe. Positron emission tomography with fluorodeoxyglucose imaging revealed positive tumor uptake (maximum standardized uptake value=8.8). Bronchoscopy yielded no specific histological findings and no bacteriological findings. Percutaneous transthoracic lung biopsy revealed epithelioid granuloma but no acid-fast bacilli were detected. The patient received isoniazid, rifampin, ethambutol, and pyrazinamide for the treatment of "tuberculoma". Five weeks after the patient was admitted, numerous mycobacterial colonies were detected on a bronchial washing fluid culture. These colonies were subsequently identified as Mycobacterium intracellulare. A final diagnosis of M. intracellulare pulmonary disease was made, and the patient's treatment regimen was changed to a combination therapy consisting of clarithromycin, rifampin, and ethambutol.