Giant hepatic artery aneurysm is a very rare vascular lesion, but can be detected incidentally during abdominal imaging. We report the sonographic and computed tomography (CT) features of a giant hepatic artery aneurysm in a 52-year-old woman presenting with vague abdominal discomfort. This report illustrates that a giant hepatic artery aneurysm can manifest as an incidental large mass in the porta hepatis, and we discuss the role of sonography and CT in the diagnosis of the lesion and review the natural history and clinical presentation of hepatic artery aneurysm.