Background: Online exercise interventions can improve access to tailored programmes for individuals with intellectual disabilities (including Down syndrome). This paper aimed to describe best practices and provide recommendations for online physical activity or exercise programmes for this population. Method: Two research teams with extensive experience delivering online physical activity and exercise interventions in > 240 individuals with intellectual disabilities, combined with input from participant/caregiver dyads, describe adaptations to online delivery of programmes with regard to development, recruitment, data collection, intervention delivery, communication and staff requirements, based on two specific online programmes. Results: Adaptations to an online delivery are necessary for every aspect of exercise interventions for individuals with intellectual disabilities. All phases benefit from input from the community. Conclusion: When the appropriate adaptations are made for online delivery, as described in this paper, online physical activity or exercise interventions can be highly successful for individuals with intellectual disabilities.