Blunt trauma to the abdomen is an exceptional cause of portal vein thrombosis. To our knowledge, 8 cases have been reported in the literature. When thrombosis of the portal vein occurs, a complete search for all the known main causes must be carried out before entertaining this diagnosis. Other causes may be cirrhosis, tumors and inflammation of the abdomen, coagulation disorders and hematologic diseases including latent myeloproliferative syndrome. We report a case in a 25-year-old man with an uneventful past history who presented with thrombosis of the portal vein after a violent blunt trauma which occurred during a rugby play. In this young man, none of the other potential causes was found, in particular bone marrow culture on medium with low growth-factor concentration allowed us to eliminate a latent myeloproliferative syndrome. The only triggering factor remaining was the recent abdominal trauma. After an 18-month follow-up, no other element has been observed which could have caused thrombosis of the portal vein.