Women’s employment remains highly sensitive to childcare constraints, making childcare availability a critical lever for supporting mothers’ labor force attachment. We study the effects of expanded full-day programming in Head Start, using the 2016 federal funding initiative that targeted grantees with low full-day enrollment. Linking administrative program data, geo-coded center locations, and household data on employment, we estimate a difference-in-differences design by comparing mothers of young children in treated and untreated areas. The policy increased full-day enrollment by 19 percent and raised single mothers’ employment (1.9%), hours (2.5%), and earnings (6.5%). Results show that extending program duration meaningfully improves maternal labor market outcomes.