Septic pylephlebitis is usually a complication of intraabdominal infection in the region drained by the portal venous system. We report two cases of portal and mesenteric venous thrombosis associated with Fusobacterium necrophorum bacteremia, which did not show any obvious intra-abdominal source of infection with noninvasive imaging procedures. In one case, early anticoagulation treatment was associated with repermeation of the portal vein and its right branch. As in Bacteroides bacteremia, portal and/or mesenteric venous thrombosis should be searched for in case of Fusobacterium bacteremia of unknown origin. Repermeation of the portal vein and relief of extrahepatic portal hypertension can be achieved in these cases with early anticoagulation.