This paper describes the development, implementation and preliminary evaluation of the Reaching Educators and Children (REACH) program, a training and coaching intervention designed to increase the capacity of early childhood teachers to support children's social and emotional development. We evaluated REACH with 139 teachers of toddler and preschool classrooms. Teacher attendance and survey results suggest that teachers were highly satisfied with the training and materials. Data from classroom observation scales conducted pre- and post-REACH implementation suggest significant improvements in the sensitivity of teachers' interactions with children in the classroom, and increased teacher use of targeted social and emotional supports (such as teaching children to resolve conflicts). Further, data from observations of children's classroom behavior suggest increases in children's prosocial behaviors and small but significant decreases in verbal aggression. These findings provide preliminary evidence that the REACH program may be effective in building teachers' capacity to support social-emotional development of young children, and point to the need for additional research.