Even though after-school childcare arrangements are a significant matter for working mothers in the United States, only formal childcare has been recognized as relevant by researchers. Therefore, this study aims to find the association between different types of after-school childcare arrangements (after-school programs, relative, parental, self-care, and combination of care) and low-income working mothers’ labor supply, including their working hours and months, as well as their availability for regular job shifts and training/school, with special attention to their race/ethnicity. The study employed the Ordinary Least Square regression analysis and utilized the National Household Education Survey Programs: After-School Programs and Activities (2005). The results showed that White and Hispanic mothers using relative care reported longer working hours than mothers of the same ethnic group who used other types of care. Hispanic mothers using parental (spousal) care also reported fewer working months than Hispanic mothers using relative care. Implications for policy, social work practice, and research are discussed along with limitations, including the cross-sectional design of the study.