Protein C and S, vitamin K-dependent proteins, are blood coagulation inhibitors. Their deficiency causes systemic thrombosis. A 35-year-old man who developed superior mesenteric venous thrombosis and portal vein thrombosis showed markedly decreased protein C and S levels. The therapeutic modality of this thrombosis associated with protein C and S deficiency is still debated. We treated this patient with systemic anticoagulation and long term total parenteral nutrition without surgical intervention.