This article examines changes in parental labor supply in response to the unanticipated closure of schools following the onset of the COVID-19 pandemic in the United States. The authors collect detailed daily information on school closures at the school-district level, which they merge to individual-level data on labor supply and sociodemographic characteristics from the monthly Current Population Survey spanning from January 2019 through May 2020. Using a difference-in-differences estimation approach, the authors find evidence of non-negligible labor supply reductions. Having a partner at home helped offset the negative effect of school closures, particularly for maternal employment, although respondents' job traits played a more significant role in shaping labor supply responses to school closures. Overall, the labor supply impacts of school closures prove robust to identification checks and to controlling for other coexistent social distancing measures. In addition, these early school closures seem to have had a long-lasting negative impact on parental labor supply.