This study examines the effects of intrapersonal caregiver characteristics on infant/toddler social-emotional outcomes and if these relations are mediated by the level of sensitive and responsive care within the context of center-based child care. Data come from 111 caregivers and 114 children from 41 Early Head Start and community infant/toddler classrooms in California. Path analyses estimated direct and indirect effects of caregiver emotion regulation and internal representations of care and revealed that sensitive and responsive care mediated the association between these intrapersonal caregiver characteristics and children's social-emotional outcomes. Results suggested that caregivers' ability to form a positive affective and relational community within the group of infants and toddlers was more important than their ability to attend to children solely on an individual basis. The study provides evidence for the value of developing early childhood professional development strategies aimed at helping caregivers understand the importance of child-level and group-level attunement as well as recognize child- and group-level indicators of security, regulatory capacity, engagement, and sense of community. (author abstract)