We report a case of trauma causing the formation of a pseudoaneurysm of the proper hepatic artery. The preoperative computed tomographic (CT) finding of decreased enhancement of the left lobe of the liver was suggestive of ischemia or infarct secondary to hepatic arterial injury. A proper hepatic artery pseudoaneurysm was discovered on a follow-up postoperative CT. Retrospective review of the preoperative CT revealed the presence of a focal hematoma and an indistinct proper hepatic arterial segment at the site of the pseudoaneurysm. Although the pseudoaneurysm was not discovered intraoperatively, it was later confirmed by angiography and duplex ultrasound. The patient demonstrated extensive necrosis in the left lobe of the liver on the follow-up CT. The nature of the liver perfusion abnormalities that led to these findings is discussed.