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.