An unusual cause of the thoracic outlet syndrome secondary to an anomalous subclavius muscle insertion that was diagnosed in a middle-aged woman who had neck and upper limb pain with parenthesis in her right hand is presented. The patient was successfully treated by surgical muscle resection. The importance of this case is the uncommon cause of the compression. We would like to emphasize the relevance of considering the thoracic outlet syndrome for the differential diagnosis of cervical and cervicobrachial pain.