Effectively engaging individuals with developmental disabilities is essential to Extension's diversity and inclusion mandate. The Centers for Disease Control and Prevention has reported that over 6 million individuals have developmental disabilities. We in Extension have the potential to include a proportionate number of individuals with developmental disabilities in our programs wherever we serve. The Developmental Disabilities Training Series, an online or in-person professional development series, prepares Extension personnel and volunteers with the knowledge, skills, and confidence needed to design and implement community-based programs for this clientele. The series includes five courses, fact sheets, and resource materials.