BACKGROUND: The aim of this study was to evaluate the prevalence of folic acid (FA) prescription to prenatal and postpartum women who have also been prescribed antiepileptic drugs (AED) in Japan. METHODS: The data set used in this study included women covered by health insurance between 2005 and 2016. The prevalence of FA prescriptions between 180 days before pregnancy and 180 days postpartum was determined from a large administrative database, with the FA prescription classified according to dose and timing. RESULTS: For 33,941 women meeting our eligibility criteria, the mean maternal age at delivery was 32.3 years. At least one AED was prescribed to 225 of 33,941 women between 180 days before pregnancy and 180 days postpartum. FA was prescribed to 32 of 225 women (14.2%) during the same period. FA was prescribed to 8.8% of women with AED within 90 days before pregnancy and to 19.8% during the first trimester. FA was prescribed to 10.9% during the first 30 days after conception, all of whom were prescribed FA before the pregnancy. The maximum FA dose prescribed within 90 days before pregnancy was 5 mg/day for 5 of 12 women (41.7%) and >5 mg/day for 4 of 12 women (33.3%). The maximum FA dose prescribed during the first trimester was 5 mg/day for 14 of 22 women (63.6%) and >5 mg/day for 8 of 22 women (36.4%). CONCLUSIONS: The concurrent prescription of FA with AEDs in Japan was an uncommon therapeutic approach both before and during pregnancy.