An infected (mycotic) aneurysm of the visceral arteries is an uncommon entity, which may arise from a secondary infection of a preexisting aneurysm or be due to degeneration from a primary infection. Mycotic aneurysms require prompt recognition and definitive treatment; otherwise, there can be devastating morbidity and mortality. We present the case of a 51-year-old female with HIV and Crohn's disease who presented with subacute abdominal pain, nausea, and vomiting and was found to have an ultimately fatal mycotic aneurysm of the superior mesenteric artery. In addition, we discuss the characteristic imaging features of mycotic aneurysms on computed tomography and magnetic resonance imaging.