We report a case of Mycobacterium abscessus infection complicated with diabetes mellitus. A 38-year-old man with diabetes mellitus as an underlying disease, was admitted to our hospital because of a productive cough. He had had pulmonary tuberculosis two years before. Chest radiography revealed infiltration in both lung apices and chest CT showed a cavitary lesion in the left upper lobe. Gaffky 2 was found on a sputum smear. However, in the examination of PCR on sputum, not only M. tuberculosis but M. avium complex was negative, and repeated cultures of sputum were positive for M. abscessus. On the basis of the diagnosis of an M. abscessus infection, the patient was initially treated with amikacin, imipenem/cilastatin and levofloxacin during hospitalization while receiving insulin for diabetes mellitus. The smear and culture of sputum became negative for Mycobacterium, and the findings of chest radiography and chest CT improved. After discharge, treatment was continued with clarithromycin and levofloxacin. It is considered that the choice of effective drugs and the additional treatment of an underlying disease are very important for the treatment of a Mycobacterium abscessus infection.