In adults, mesenteric venous thrombosis with extension into the portal system is a known complication of total proctocolectomy with pouch ileoanal anastomosis. Although frequently reported in adults, this complication is rare in pediatric patients undergoing this operation. We report 2 cases of adolescent patients with ulcerative colitis who experienced portal vein thrombosis after this procedure. Both were treated with systemic anticoagulation therapy with complete resolution of their clots. We recommend that mesenteric/portal venous thrombosis be considered in the differential diagnosis in any child presenting with fever, abdominal pain, and leukocytosis after restorative proctocolectomy with ileal pouch anastomosis and that imaging obtained to evaluate abdominal complaints in this population be directed toward ruling out this complication. © 2010 Elsevier Inc. All rights reserved.