Research Findings: Home-based child care accounts for a significant proportion of nonparental child care arrangements for young children in the United States. Yet the early care and education field lacks clear models or pathways for how to improve quality in these settings. The conceptual model presented here articulates the components of high-quality support to child care providers; related factors; and hypothesized provider, family, and child outcomes. The model is based on a literature review of research on home-based child care, home visiting, early childhood mental health consultation, coaching, and family services. We hypothesize that high-quality support to home-based child care that offers relationship-based services focused on quality caregiving (individual home visiting and group supports such as training and networking) and sustainability (materials, equipment, referrals) is most likely to positively impact quality caregiving for children and families. Practice or Policy: Current federal efforts and policy initiatives to increase the supply and quality of infant-toddler child care focus on the development of systems that support home-based providers. The conceptual model of high-quality support described here will inform future program development and research on how to improve quality in home-based child care for the millions of low-income children in these settings. (author abstract)