Half of all infants and toddlers receive care in nonparental settings, such as centers and family child care (FCC) homes. On average, infants and toddlers spend more hours per week in care than preschoolers do. Yet infant-toddler care has been identified as lower quality than care for older children, suggesting that professional development (PD) for caregivers could improve care and interactions. Available research on coaching and PD has focused on teachers for preschool or school-age children, with very few studies examining PD strategies for infant-toddler caregivers. The goal of this brief is to describe the implementation of the We Grow Together (WGT) Professional Development System during a field test conducted in late fall 2018 to spring 2019. WGT is a research-based PD system for caregivers working with infants and toddlers in center-based care and FCCs. The field test examined implementation with teachers and caregivers of infants and toddlers and their PD providers in Early Head Start, FCCs, and community-based child care settings.