Inferior mesenteric artery (IMA) aneurysms are the rarest of all visceral artery aneurysms, with most resulting from atherosclerotic disease. Mycotic IMA aneurysms are exceptionally uncommon and only 2 cases have been reported in the literature. Coagulase-negative staphylococcus (CNS) is often considered a contaminant; however, increasing reports of certain strains causing endocarditis are becoming more prevalent. We report a case of a mycotic IMA aneurysm, in the setting of native valve endocarditis caused by Staphylococcus simulans, a strain of CNS. To our knowledge, this is the third report of a mycotic IMA aneurysm, and the first account of this usually benign pathogen leading to aneurysmal degeneration in this location.