Venous thrombosis can complicate inflammatory bowel diseases, both in adult and pediatric patients, and a few adult cases of thrombotic storm, ie, thrombosis at multiple sites occurring over a period of a few days to a few weeks, have been described. However, venous thrombosis as the first manifestation of an inflammatory bowel disease is extremely rare. We report the case of a 14-year-old girl presenting with ascites and marked hypertransaminasemia resulting from hepatic vein occlusion (Budd-Chiari syndrome). Despite anticoagulant therapy, in the following days she developed criteria suggestive of thrombotic storm to include cerebral vein, right atrial thrombosis, and bilateral pulmonary embolism. Thrombolytic treatment with recombinant-tissue plasminogen activator was started, with resolution of all venous thromboses and without bleeding complications. Additional examinations revealed a severely active ulcerative pancolitis, which did not respond to medical treatment and required surgery. No thrombophilia abnormality nor other risk factors for thrombosis were detected. We conclude that an underlying inflammatory state, such as ulcerative colitis, should be suspected in pediatric patients with venous thrombosis storm.