A 69-year-old female was admitted to our hospital for further examination of an intrahepatic mass which had been found while undergoing a complete physical examination. The mass measured 4 cm in size and was located in the medial segment (S4) of the liver. On computed tomography (CT), S4 was observed to be 'atrophied' and was well enhanced segmentally. A celiac angiogram showed segmental staining, and a transarterial portogram demonstrated portal stoppage of S4 from the left branch. However, no segmental intensity difference was seen on magnetic resonance imaging (MRI). An aspiration biopsy showed adenocarcinoma and thus an operation was performed under a tentative diagnosis of intrahepatic cholangiocarcinoma. The postoperative diagnosis of the tumor was combined hepatocellular and cholangiocellular carcinoma. However, no histological abnormality was seen in S4, contrary to the expectation of Zahn's infarct. In this study, we discuss the mechanism and imaging findings of Zahn's infarct, the possible reasons as to why no pathological change was seen in S4, as well as stress the rarity of reports on Zahn's infarct in cases of portal thrombus due to hepatocellular carcinoma.