Mycobacterium celatum is a slow-growing, non-tuberculous mycobacterium (NTM) and a rare cause of infection in humans. Infection occurs primarily by inhalation or direct inoculation from environmental sources, and this pathogen has been reported to cause localized infections in the lungs and lymph nodes of both immunocompetent and immunocompromised patients, and disseminated disease in immunocompromised patients. Here, we present a case of pulmonary infection with M. celatum in an immunocompetent 68-year-old male with clinical features similar to tuberculosis. The patient initially developed palpitations, worsening fatigue, night sweats, dyspnea, productive cough, and weight loss. Computed tomography angiogram of the chest revealed a right upper lobe pulmonary artery embolus and extensive biapical fibronodular cavitary densities. Two separate sputum samples were positive for acid-fast bacilli (AFB) and sputum cultures were positive for M. celatum. The patient responded well to treatment with clarithromycin, ciprofloxacin, and ethambutol. We advise physicians to consider M. celatum infection in the differential diagnosis of patients with symptoms and radiographic and microbiologic evidence suggestive of NTM pulmonary infection.