We evaluate a spillover effect of the Japanese public long-term care insurance (LTCI) as a policy to stimulate family caregivers’ labor force participation. Using nationally representative data from 1995 to 2013, we apply difference-in-difference propensity score matching to investigate the spillover effect in two periods: before and after the introduction of the LTCI in 2000 and before and after its major amendment in 2006. Our results show that the LTCI introduction has significant and positive spillover effects on family caregivers’ labor force participation and the effects vary by gender and age. In contrast, the LTCI amendment is found to have generally negative spillover effects on their labor force participation. We draw attention to these spillover effects, as expanding labor market supply to sustain the economy would be a priority for Japan and other rapidly aging countries in the coming decades.