An accessory head of the biceps brachii muscle was found in the left arm of a 65-year-old male cadaver during routing dissection studies. It originated from the brachialis muscle and medial intermuscular septum. The arterial supply was provided by a short muscle branch of the brachial artery and its neural innervation by a short thin branch of the musculocutaneus nerve. In general, the accessory head originates from the upper-medial component of the brachialis muscle, whereas it stemmed from the lower-medial component in this case.