Recent studies have focused on the effects of low doses of Bisphenol A (BPA) on the central nervous system, which may prevent sexual dimorphism of the brain in rodents. To assess sensitivity to BPA, mother–infant behaviors in the cynomolgus monkey were studied longitudinally after treating the mothers with low-dose BPA during pregnancy. Mother–infant interaction was observed for 6 months after the birth of the infants. In conclusion, male offspring of BPA-treated females showed female-like behavior patterns. Prenatal BPA exposure altered infant behavior in the early stages of mother–infant interaction, and male infants were affected more seriously than females.