Japan has maintained measles elimination status since 2015. However, sporadic outbreaks of measles have been continuously reported. Here, we report a case of a measles-infected postpartum mother and infant in Japan. A 28-year-old Japanese woman, who had previously received a dose of the measles vaccination, experienced fever 5 days postpartum. Subsequently, a maculopapular rash appeared, and she was diagnosed with measles. Moreover, her baby developed a fever and maculopapular rash on the 13th day of life, 2 days after postexposure prophylaxis with intravenous immunoglobulin, and was also diagnosed with measles. Both showed full recovery. This case suggests that measles can still be a threat in a measles-eliminated country, and the administration of two doses of measles vaccination to women prior to childbearing age is crucial to protect newborns from measles.