A model for designing and implementing evidence-based in-service professional development in early childhood intervention as well as the key features of the model are described. The key features include professional development specialist (PDS) description and demonstration of an intervention practice, active and authentic job-embedded practitioner opportunities to learn to use the practice, opportunities for practitioner reflection on the understanding and mastery of the practice, PDS coaching, mentoring, or performance feedback during in-service sessions, PDS follow-up supports to reinforce initial practitioner in-service learning, in-service training and follow-up of sufficient dosage to produce sustainable change, and the inclusion of as many key features as possible as part of the provision of in-service training afforded early childhood practitioners. The need for systematic reviews and meta-analysis of early childhood in-service professional development studies is noted to identify which key features in which combinations under which conditions are most effective.