A variation of the trapezius muscle was observed in a Korean female adult cadaver during routine student dissection. The lateral, upper three-fourths of the descending portion of the trapezius muscle were separated from the remainder of the muscle. This single, isolated bundle fused above the insertion of the midpoint of the clavicle, and attached to the clavicle as a separate tendon. The remaining descending portion inserted into the clavicle and scapula as usual. This abnormal muscle bundle is considered as a variant of the cleido-occipitalis cervicalis, and formation of this variation is discussed based on the embryological development of the relative muscular structures.