Abstract: This study examines the impact of a child’s cancer diagnosis on parents’ labor supply. Using data from South Korea’s National Health Insurance System, we find heterogeneous effects based on gender, parents’ relative income, and employment type. Specifically, we observe that mothers experience a significant decline in employment and income following their child’s cancer diagnosis, while fathers’ employment and income remain relatively unchanged. The decrease in fathers’ labor supply is only observed among those with lower income compared to their spouse, whereas mothers’ employment decreases regardless of relative income. Furthermore, we find that self-employed mothers are less affected compared to wage workers, while the effects on fathers are generally minimal.