We report a case of dual nontuberculous mycobacterial infections complicating an open distal radius and ulna fracture after polytrauma in a 35-year-old man. There was persistent wound discharge after definitive fixation of this fracture, but microbiological cultures did not yield any organism. The patient underwent multiple debridement, and subsequent tissue grew Mycobacterium chelonae and Mycobacterium fortuitum. Despite appropriate chemotherapy and surgical debridement the infection persisted until radical bone excision and tissue debridement were done. This case indicates that nontuberculous mycobacterial infections should be considered when conventional microbiological assays fail to identify the infecting agent in suspected osteomyelitis following open fracture. A combination of radical debridement, including removal of infected bone, and prolonged antimicrobial therapy are required to eradicate the infection completely.