This paper exploits variation resulting from a series of federal and state Medicaid expansions between 1977 and 2017 to estimate the effects of children’s access to public health insurance on the labor market outcomes of their mothers. The results imply that the extended Medicaid eligibility of children leads to positive labor supply responses at the extensive and intensive margins of single mothers and to negative labor supply responses at the extensive margin of married mothers. The analysis of mechanisms suggests that extended children’s Medicaid eligibility positively affects take-up of Medicaid and health of children.