We describe the presence of an accessory subscapularis muscle observed bilaterally in a human anatomy laboratory. The muscle originated from the mid-region of the lateral subscapularis inserting into the proximal humerus with the tendon of the subscapularis. The axillary and lower subscapular nerves coursed between the observed muscle and the subscapularis. The presence of the muscle has potential to entrap the axillary nerve and the lower subscapular nerve.
