Bilateral insertion abnormality of pectoralis minimus (sterno-costo-coracoidian muscle) muscle was examined. The variant muscle was lying under the pectoralis major muscle and was medial to the pectoralis minor muscle. This muscle started from the first costal cartilage to the manubrium sterni and ended in the upper surface of the shoulder joint on the right side. On the opposite side, it took origin from the second costal cartilage to the manubrium sterni and the second costochondral joint, afterwards became a tendinous structure and divided into two on the coracoid process. The thicker part ended on the upper surface of the articular capsule of the shoulder joint, the thinner part inserted on the lateral third of inferior part of clavicle and fascia of subclavius muscle.