During routine dissection for first M.B.B.S. students on 65 years donated embalmed male cadaver in the Department of Anatomy, K. J. Somaiya Medical College, we observed an additional insertion of left brachialis muscle. The origin of the accessory muscle belly was from the anteromedial surface of the shaft and the medial supracondylar ridge of the lower end of the humerus. The accessory muscle slip merged with the tendon of pronator teres and got inserted on to the upper one third of the lateral surface of the shaft of the radius. The accessory muscle belly of the brachialis muscle was innervated by musculocutaneous nerve. There were no associated altered anatomy of the blood vessels observed in the specimen. The right upper limb of the same cadaver was normal. The photographs of the variations were taken for proper documentation and for ready reference. The knowledge of such type of variation is clinically important for Anatomists, Neurologists, Radiologists, Surgeons Plastic surgeons and Orthopedicians.