The peroneus quartus is an accessory peroneal muscle seen in man. The term 'peroneus quartus' is often used to refer one or several of the accessory peroneal muscles. In this case, we report an unusual type of peroneus quartus which was originating from the muscular portion of the peroneus brevis and inserting onto the peroneus longus tendon. The clinical implications are emphasized with the morphological significance and literature review. The orthopedic surgeons and radiologists should be aware of the possible presence of this muscle not only because of its associated pathology, but also for its potential use in plastic surgeries.