Klippel-Trenaunay syndrome (KTS) is a rare, clinically variable congenital disorder involving capillary malformations, soft tissue or bone hypertrophy, and venous malformations or varicose veins. We report a 28-year-old man who presented with a hypertrophic right arm as well as markedly increased ipsilateral axillary hyperhidrosis and erythematous patches on the back, chest, and arm. This case of KTS is unusual because our patient presented with a markedly increased unilateral axillary hyperhidrosis ipsilateral to the hypertrophic limb.