BackgroundFamily carers play a crucial role in supporting the health and well-being of people with intellectual disabilities. Given their role and responsibilities, many family carers experience significant and ongoing stress and mental health difficulties. Programmes and interventions which provide training and support to family carers have been shown to have a positive impact on levels of stress and quality of life. However, these are often face to face which can create barriers to full participation. Online interventions have been shown to offer flexibility in delivery compared with traditional face-to-face approaches. The primary objective of this study is to determine the feasibility of delivering the Carers-ID online intervention, while the secondary outcome is improved mental health in family carers of people with intellectual disabilities.MethodsFamily carers (n = 120) will be randomised to receive the intervention (n = 60) or assigned to a wait-list control (n = 60) group. The intervention (www.Carers-ID.com) consists of 14 modules which cover topics including the following: promoting resilience, providing peer support, reducing anxiety, managing stress, accessing local supports and managing family conflict and information for siblings who are carers. The intervention has been co-produced with voluntary sector organisations and family carers and tested for acceptability. Primary outcomes for this study include acceptability and feasibility of the outcome measures, recruitment, participation and retention rates and effect sizes. Secondary outcomes will be completed at three time points (baseline, following intervention completion and 3 months after completion). These include the following: the Depression, Anxiety and Stress Scale, the Warwick–Edinburgh Mental Well-being Scale, the Resilience Scale and the Social Connectedness Scale Revised. Participants (n = 12) who have taken part in the intervention arm of the research will be invited to participate in semi-structured interviews as part of the process evaluation.DiscussionThe Carers-ID intervention provides an online resource for family carers to support their mental health and well-being and promote their resilience. It represents an affordable and accessible means of delivering such support. Testing the feasibility of the intervention and related trial procedures is required to determine whether a full-scale randomised controlled trial to evaluate the intervention’s effectiveness is warranted.Trial registrationClinicalTrials.gov: NCT05737823