As aging is occurring at a rate never before seen in South Korea, the present study examines the predictors of mental health in a nationally representative sample of older adults (n = 4,155), drawn from Wave I of the Korean Longitudinal Study on Aging. Findings show that sociodemographic factors, chronic health conditions, level of cognition, and social activities contribute to life satisfaction and mental health among older adults in South Korea. Life satisfaction is mainly determined by sociodemographic factors for both women and men. Compared to women, men's levels of depression and life satisfaction appear to be more influenced by their health, cognitive functioning, and social activity participation. Implications for practice and policy are discussed.