The purpose of this article is twofold: (1) to describe the ADA Trainer Network (ADA TN), a capacity building program designed to build knowledge, alter beliefs and change practices around disability inclusiveness across a range of social participation spheres, and (2) to investigate the effectiveness of the ADA TN program. Based on a capacity building approach, the program aimed to extend the reach of disability efforts by engaging key disability agents (ADA TN members) to build awareness and change actions or behaviors to promote disability inclusiveness within their local communities. In addition to the detailed information about how the program was implemented and evaluated, data collected from the training program were analyzed. A total of 6,250 end-users participated in the 337 training sessions delivered by 413 ADA TN members. Findings from the pre-/post-training survey indicated significant increases in knowledge and intention to act among end-users participating in the trainings offered by ADA TN members. Based on the current capacity building challenges in the disability field, issues for future iterations of the ADA TN program are discussed.