Klippel-Trenaunay-Weber syndrome is characterized by cutaneous hemangiomas, varicosity and bony hypertrophy of extremities. Urinary tract hemangiomas may occur in 3 to 6% of these patients. This work intends to report a case of a patient with a huge vesical hemangioma, who presented this syndrome. A 5 year-old boy with Klippel syndrome sought our services due to 3 episodes of gross hematuria in the past 30 days. Excretory urography and computerized tomography were performed, indicating the presence of a swelling in vesical dome. An exploratory cystotomy was conducted and the dark colored mass in vesical dome was excised by partial cystectomy. The histopathologic finding confirmed that it was a vesical hemangioma. Though rare, urinary tract hemangiomas must always be considered in patients with Klippel-Trenaunay syndrome.