The pectoralis minor is a triangular muscle that arises from the third, fourth, and fifth ribs, close to their cartilages. Its fibers pass upward and laterally, and its tendon of insertion is attached to the upper surface and the medial border of the coracoid process, near its tip.

When the muscle is in action it draws the scapula downward and forward, and depresses the shoulder. It is supplied by the medial pectoral nerve. The greater the pectoralis minor lies below the pectoralis major, but the lower part of its infero-lateral border appears on the side of the thorax below the pectoralis major; its insertion is concealed by the anterior fibers of the deltoid.