Infections due to Listeria monocytogenes usually occur in pregnant women, in elderly or immunocompromised patients. We report the case of an immunosuppressed woman who had been hospitalized for a meningoencephalitis due to L. monocytogenes. She was operated on for an abdominal hemorrhagic shock due to a ruptured mycotic aneurysm of the inferior mesenteric artery. Arterial aneurysms due to this germ are rare and occur on large arteries. Only 17 cases have been previously described in the literature and just one concerning a mesenteric artery.