Abstract Background Attention deficit hyperactivity disorder (ADHD) is underdiagnosed in the UK and the assessment and diagnosis pathway often involves a general practitioner (GP) referral to secondary care services. GPs’ levels of knowledge and understanding about ADHD is often a significant barrier in patients accessing care. The development of an online education resource could improve GPs knowledge of ADHD and optimise appropriate referrals. Involving end-users in co-creating interventions may enhance their clinical utility and impact routine clinical practice. However, there is limited published evidence describing how to meaningfully involve stakeholders in both the design and development components of co-production. Method We report a step wise, co-production approach towards developing an online ADHD education intervention for GPs. Preparatory work highlighted the relevant topics to be included in the intervention, from which educational videos were then developed. Workshops were then conducted with GPs, leading to further refinement of the video content and subsequently the final intervention. A pilot usability study (n = 10 GPs) was then conducted to assess the intervention’s acceptability, feasibility and accessibility. Results The development of the online intervention was greatly facilitated by the involvement of GPs. Having a co-production development process ensured the consistent adaptation of the intervention to meet GPs’ needs. The usability study showed that the content of the intervention was suitable, easily accessible, engaging and delivered at an acceptable level of intensity, validating the development approach taken. Conclusion While further studies are needed to evaluate the efficacy of the developed intervention, preliminary findings demonstrated that it was acceptable and well received. The importance of co-development was highlighted in developing an intervention that addresses specific needs for GPs. This development approach may be useful for other researchers and developers of clinical interventions.