Abstract Funding Acknowledgements Type of funding sources: Other. Main funding source(s): Department for the Economy, Northern Ireland Introduction Controllable cardiovascular disease (CVD) risk factors are often initiated in the family home, yet risk reduction is seldom targeted toward families. Participatory design of eHealth interventions with end-users has potential to increase acceptability and adherence of such interventions. Despite their shared risk of developing CVD, few eHealth interventions target both parents and children at CVD risk. Therein lies an evidence gap; the need for coproduction of a family-based eHealth intervention aimed at early CVD prevention. Purpose The aim of this study was to identify the perceptions of families towards the design, functionality and acceptability of an eHealth, family-based, CVD prevention intervention. Methods Thee online focus groups comprising six families were conducted between April and May 2021. Families consisted of at least one parent who met CVD risk factor criteria, and at least one child aged five to 17 years. Content analysis and narrative synthesis were used to identify categories and subcategories regarding development of and engagement with the proposed intervention. Additionally, quantitative, and demographic measures were used to determine psychosocial and health profiles. Results Three categories were identified from the focus groups: 1) previous experiences of using health-related apps or devices 2) expectations of a newly developed eHealth family-based CVD prevention intervention 3) motivators for engagement with the intervention Goal setting, rewards, accountability, adaptability, recording achievements and competition were considered crucial motivators for engagement for both parents and children. Participants welcomed the intervention, and advised they would prefer a free, personalised, easy-to-use, non-time-consuming intervention, with multiple content formats, and additional information available should they seek to access it. Parents conveyed satisfactory general self-efficacy and quality of life, low anxiety and depression and high perceived social support. Conclusions Overall, families were constructive and forthcoming towards the idea of an eHealth, family-based CVD prevention intervention. These findings informed a prototype of a family-based eHealth intervention aimed at early CVD prevention. The prototype is currently being developed with plans for piloting via a randomised controlled trial in the home environment, by families as an early intervention for the prevention of CVD.