Klippel-Trenaunay syndrome is a congenital capillary-venous vascular malformation characterized by malformation of the capillaries, soft tissue and bone hypertrophy and atypical varicosities. Klippel-Trenaunay syndrome often affects the lower extremity but can also involve arms, trunk, head, neck, abdominal and pelvic organs, and central nervous system. Deep venous system anomalies are important in directing the treatment of these cases. In cases of deep vein hypoplasia, marginal vein can be resected since hypoplastic deep veins can spontaneously dilate to almost normal dimensions after marginal vein resection. In cases of deep venous aplasia, the embryonal vein can be the main drainage vein of the leg and the resection is unlikely. In this article, we present a case of a 20-year-old male with Klippel-Trenaunay syndrome who had right leg diameter increase, port-wine stain appearance, and venous ulcer.