Venous thrombosis and thromboembolism appear to occur more often in patient with inflammatory bowel disease (IBD). The cause of thrombotic complications in IBD is generally considered to be associated with hypercoagulable conditions. Its prevalence rate ranges from 1% to 8% in clinical studies and rises to 39% in autopsy, but the renal vein thrombosis is very rare complication in ulcerative colitis patient. A 24-year-old man presented with intermittent abdominal pain and hematochezia for 6 months and recently developed pitting edema for few weeks. He was diagnosed as severe ulcerative colitis involving whole colon combined with thrombosis in both renal veins by colonoscopy and computed tomography scan of abdomen. We used steroid for the treatment of ulcerative colitis and both intravenous lower molecular weight heparin and warfarin for renal vein thrombosis. His symptoms were improved after treatment and maintained with mesalazine and warfarin. Follow-up abdominal CT scan showed complete resolution of both renal vein thrombosis. Currently he has been followed up for 2 years with oral mesalazine.