The brachial plexus palsies secondary to nonunion of the clavicle fracture are extremely rare. The nonunions are hypertrophic and usually in the middle third of the clavicle. Hypertrophic callus produced during healing process will cause a compression of the neurovascular bundle. This lesion requires operative treatment for decompression of the brachial plexus and internal fixation of nonunion. We present a case of delayed brachial plexus palsy due to nonunion and excessive callus formation of a clavicular fracture.