The latissimus dorsi muscle is a flat and triangular muscle that covers the lumbar region and the inferior part of thorax. This muscle supplied by thoracodorsal nerve(C6, C7,C8), a branch of posterior cord of brachial plexus. Many reports showed that a muscular axillary arch , flat muscle arising from lateral border of latissimus dorsi , may be seen in 7% of the population, but there is little information about the innervation of this part. This report deals with dissecting the axillary region of a 41 year-old male cadaver in which we observed a muscular axillary arch was innervated by a single nerve branch of pectoral loop