Background: Persons with intellectual disabilities (ID) experience a wide range of health problems. Research is needed on teaching persons with intellectual disabilities about their health to promote self-advocacy. This study used a RCT to evaluate a health knowledge training program for adults with intellectual disabilities and verbal skills. Methods: Participants were randomly assigned to training (n = 12) or no training control (n = 10) groups. Topics included key body organs, systems, functions, health maintenance and illnesses. Participants played a game answering questions (e.g. "What does the heart do?"). Instruction involved visuals (e.g. PowerPoint slides), cueing, modelling and feedback. The control group received pre-, post- and follow-up tests as the training group. Results: The training group had significantly higher overall post-test and follow-up health knowledge test scores than the control group. Conclusions: Health knowledge training is one step in promoting health self-advocacy and better health in persons with intellectual disabilities.