Utilizing data from South Korea’s National Health Insurance Database, which covers the entire population, this study investigates the health-seeking patterns of North Korean defectors in South Korea, focusing on mental health issues. We find that female North Korean defectors utilize mental healthcare services significantly more than male defectors and more than their matched counterparts among either South Korean natives or other immigrants. Regarding the long-term effects of residing in South Korea, indicators of both the prevalence and seriousness of mental health issues do not appear to decrease over time, for up to fifteen years after migration. We recommend more active medical support and intervention by the government to alleviate the difficulty of adjustment among female North Korean defectors that arises from mental health issues.