This paper describes a report here the case of an 85-year-old man who developed pneumonia of Mycobacterium conspicuum, a rare nontuberculous mycobacterium. The patient had repeatedly complained of a bad cough and purulent sputum since December 2010. On admission in May 2011, chest x-ray showed multiple infiltrative shadows. Although mycobacterial infection was suspected from Gaffky 9 on the patient’s expectorated sputum smear, Mycobacterium tuberculosis was not detected by polymerase chain reaction (PCR). We found acid-fast bacilli also in the bronchial washing fluids, and identified the mycobacteria as M. conspicuum by Rpo B and hsp 65 methods. The patient was successfully treated with antituberculosis drugs. It is important to identify the pathogenic bacteria by frequent sputum examinations and bronchoscopy in advance of treatments.