Background: Unintentional injury is the leading cause of preventable death in children in the UK, and 0-4-year-olds frequently attend emergency departments following injuries in the home. Parenting programmes designed to support parents, promote behaviour change and enhance parent-child relationships have been shown to improve health outcomes in children. It is not known whether group-based parenting programmes have the potential to prevent unintentional injuries in preschool children. Methods: A study to develop a group-based parenting programme to prevent unintentional home injuries in preschool children, and assess the feasibility of evaluation through a cluster-randomised controlled trial. The intervention, designed for parents of children who have sustained a medically attended injury, will be developed with two voluntary sector organisations. The feasibility study will assess ability to recruit parents, deliver the programme and follow-up participants. Participants will complete questionnaires at baseline, 3 months and 6 months, and report injuries in their preschool children using a tool designed and validated for this study. Qualitative methods will assess user and deliverer perceptions of the programme. Discussion: This study will develop the first group-based parenting programme to prevent injuries in preschool children, and design tools for parent-reported injury outcomes. A key challenge will be to recruit parents to participate in a manner that is non-stigmatising, and does not result in feelings of guilt or belief that they are perceived to be a bad parent. The findings will be used to prepare a trial to assess the effectiveness and cost-effectiveness of the intervention.