A 35-year-old woman who was 14 weeks pregnant visited a gynecology hospital to undergo a surgical abortion. Although she was not jaundiced, and had no signs of hepatitis, liver function was abnormal (ALT, 100 IU/L; AST, 96 IU/L). The serum obtained was negative for markers of hepatitis A, B, and C viruses. However, based on the positive results of non-routine IgM/IgA anti-HEV and HEV RNA assays, the patient was occasionally diagnosed with sporadic acute hepatitis E. The HEV isolate recovered from the patient was phylogenetically close to known genotype 3 HEV strains circulating in Japan, with the highest identity of 93.2%. We believe that testing for hepatitis E should be routine in Japan, in cases of suspected viral hepatitis.