Purpose The aim of this study was to explore how family members perceive and support young people with traumatic physical injury during the acute phase of hospital care. Methods This study forms part of the qualitative explanatory follow-up phase of a mixed methods study. The paper reports on family members' experiences of providing support to young people 16-24 years admitted with major traumatic injury to an Australian Level 1 Trauma Centre. Semi-structured in-depth interviews with family members were conducted and transcribed verbatim. Data were managed using NVivo software, and thematically analysed. Findings Family support was determined by how family members perceived the injury. Driven by a need to protect the injured young person, family members sought to control potential emotional impacts of injury, creating a buffer between the young person and other people including healthcare professionals. Family members safeguarded the psychological well-being of the young person, in an attempt to facilitate their transition back to independence. Conclusion This study identifies iterative changes in family relationships and emotional and practical support provided by family members during the initial injury trajectory, extending understandings of the broader burden of injury. Key elements of family stress theory offer a useful framework for the development of anticipatory guidance for clinicians that are responsive to the emotional needs of patients and families, supporting the need for a family-centred care approach to managing major traumatic injury in young people.