A 36-year-old female patient was admitted to the emergency department of our hospital with symptoms and signs of pulmonary embolism. Further evaluation established the diagnosis and anticoagulant therapy was immediately started. Physical examination revealed left lower extremity edema, prominent varicose veins, greater length of the involved limb and a capillary malformation extending from the lower abdomen down to the left knee. The diagnosis of Klippel-Trenaunay syndrome (KTS) was suspected and a color duplex scan was next performed revealing derangements in the lower extremity venous system including deep venous thrombosis. KTS is a congenital anomaly characterized by capillary malformation, extensive varicosities and limb hypertrophy. Anomalies of the deep and perforator venous system coexist and predispose to thromboembolic events. Pulmonary embolism is infrequently encountered in the setting of this syndrome.