Poland's syndrome is a rare unilateral congenital anomaly characterized by the absence of the pectoral muscle and hand anomalies. By the time, new components including the absence or hypoplasia of many muscles have been identified, however, the anomalies of trapezius muscle have not been reported in patients with Poland's syndrome. The accepted etiological theory is the temporary interruption of blood supply of the subclavian artery and its branches in the early gestational period. The artery of the trapezius muscle is also one of the branches of subclavian artery. Just because of that, it is likely to trapezius muscle be affected in patients with Poland's syndrome. We are presenting a case of Poland's syndrome associated with unilateral partial absence of trapezius muscle to support this hypothesis.