Hepatocellular adenoma (HCA) is a rare primary benign tumor of the liver, which occurs predominantly in young and middle-aged women. Recently, the subclassification of HCA was proposed by the Bordeaux group. Subsequently, characteristic radiological and clinical features have been revealed in each HCA subtype. According to the previous literature, diffuse intratumoral fat deposition is a very common finding in hepatocyte nuclear factor 1α-negative HCA, but this finding has been reported in β-catenin-positive HCA in the literature for only one case. In this case report, we report the second case of β-catenin-positive HCA with MR imaging sign of diffuse intratumoral fat deposition, confirmed immunohistologically on the basis of a surgical specimen. In addition, our case showed hypovascularity and isointensity on the hepatobiliary phase which have been reported as characteristic findings in β-catenin-positive HCA. Diffuse intratumoral fat deposition can be observed in β-catenin-positive HCA, which has a greater probability of malignant transformation than other types of HCA.