Overuse myositis ossificans is considered an extremely rare diagnosis, with only a few cases reported so far. A case of a 54-year-old firefighter, involved regularly in training exercises, with bilateral myositis ossificans of the triceps, is presented. The patient had a 4 year history of painful masses at the posterior region of both arms. He never experienced any traumatic event, while physical examination revealed firm masses extending longitudinally within the lateral head of the triceps, bilaterally. The patient had painful restricted range of motion at both sides. Plain X-ray views of the humerus showed linear lobulated heterogeneous masses posterolateral. Surgical resection of both masses, which extended intramuscularly through the whole lateral triceps’ head, was performed. Histological examination confirmed the diagnosis of myositis ossificans. Myositis ossificans represents a benign, relative rare clinical entity, defined as heterotopic ossification of the soft tissues. Only 5 cases of myositis ossificans due to overuse have been described so far. The present case is unique, since it is the first one describing bilateral appearance of two masses which extended through the whole length of the lateral head of the triceps. A detailed medical history, as well as imaging examination seem to be necessary in order to establish the diagnosis. Treatment should be decided upon the stage of the lesion. For mature lesions surgical treatment is advised.