Since the early 1980s, South Korea’s total fertility rate (TFR) has continuously declined, recently reaching the 0.7 range—the lowest among OECD countries. This study develops an overlapping generations (OLG) general equilibrium model that incorporates married women’s labor supply decisions as well as their choices regarding fertility and childrearing. The model is calibrated to match average labor force participation rates of married women and fertility outcomes over the period 2015–2019. In the baseline economy, women’s fertility decisions replicate the age-specific average number of children and fertility patterns across household income groups observed in the data. When the model parameters are adjusted to reflect the gender wage gap observed in the 1990s, women’s incentives to participate in the labor market decline substantially, leading married women to increase fertility instead of labor supply. Quantitatively, however, the change in the TFR is not large enough to explain the sharp decline in fertility observed over the past three decades. This suggests that the gender wage gap alone cannot fully account for the simultaneous rise in female employment and fall in fertility in South Korea.