Digital technologies have great potential in offering interventions for people with intellectual disabilities. In this study, we aimed to co-develop a digital psycho-educational intervention, using a positive resource-oriented approach, to improve the mental well-being of people with intellectual disabilities. Using a two-phase design process, we first used a theory-guided approach to develop the content. Next, iterative consultations with an advisory group of people with and without intellectual disabilities were conducted to proceed with the digital design of the intervention. Feedback from the advisory group addressed issues regarding the intervention's accessibility, interactivity, design and content. Changes were either implemented during the meetings or presented at consecutive meetings until the design and content were deemed satisfactory by the advisory group. This approach demonstrates that people with intellectual disabilities can be included in the development of a novel digital intervention. A future intervention study should determine the practicality and acceptability of this co-developed intervention in routine practice.