Embedded in traditional culture perpetuating family-centered elderly care, informal care is still viewed as a family or moral issue rather than a social and policy issue in South Korea. Using newly available microdata from the Korean Longitudinal Study of Aging, this study investigates the effect of informal caregiving on labor market outcomes in South Korea. By doing so, this study provides evidence to inform elderly long-term care policy in South Korea, and also fills a gap in the international literature by providing results from an Asian country. Empirical analyses address various methodological issues by investigating gender differences, by examining both extensive and intensive labor market adjustments with two definitions of labor force participation, by employing different functional forms of care intensity, and by accounting for the potential endogeneity of informal care as well as intergenerational co-residence. Robust findings suggest negative effects of informal caregiving on labor market outcomes among women, but not among men. Compared with otherwise similar non-caregivers, female intensive caregivers who provide at least more than 10 hours of care per week are at an increased risk of being out of the labor force by 15.2 percentage points. When examining the probability of employment in the formal sector only, the effect magnitude is smaller. Among employed women, more intensive caregivers receive lower hourly wages by 1.65K Korean Won than otherwise similar non-caregivers. Informal care is already an important economic issue in South Korea even though aging is still at an early stage.