Fractures of the clavicle following radical neck dissection (RND) and/or radiation therapy have been previously noted in the literature. Interestingly, we experienced three cases of clavicular fracture, which were considered to have resulted from pectoralis major myocutaneous flap (PMMCF). All of these three cases had received the combined treatment of RND, PMMCF and postoperative radiotherapy on the side of fracture. In all three cases, ipsilateral lower neck received 4,500 cGy and island type of PMMCF was used for reconstruction of surgical defect in head and neck area. All fractures noted between 1 and 3 years postoperatively occurred on the medial portion of the clavicle. Devascularization after stripping of periosteum and altered mechanics of the clavicle following resection of clavicular head of pectoralis major muscle may contribute to develop this rare complication in addition to the effect of radiotherapy and RND. We present three cases of the clavicle fracture following the island type PMMCF with a review of literature.