Background: This study examines the efficacy of a staff-led, health promotion intervention entitled "HealthMatters Program: Train-the-Trainer" Model to improve health among adults with intellectual disabilities. While data support the benefits of health promotion for adults with intellectual disabilities in controlled settings, little research documents strategies to improve health and health behaviours in settings in which people work and live. Methods: Thirty-four staff in community-based organizations (CBOs) participated in an 8-[hour] training to start a 12-week health promotion programme for clients with intellectual disabilities. Participants with intellectual disabilities ("n" = 67; aged 30 and older) were randomized into an intervention (12-week exercise and health education programme) or control group. Results: Intervention group showed significant improvements in health status, knowledge, self-efficacy, and fitness. Conclusion: Results support the efficacy of a "HealthMatters Program" in CBOs to improve health among adults with intellectual disabilities. A need exists for CBOs to include health promotion in their mission and vision statement and job descriptions. (Contains 5 tables.)