Background Acquiring a traumatic injury constitutes a severe life change for the survivor, but also for the surrounding family. The paradigm of helping the family has primarily been on psychosocial interventions targeting caregivers. However, interventions including both survivor and caregivers should be an essential part of treatment, as the whole family's functional level and mental health can be affected. The current study protocol presents a manualized family intervention for families living with traumatic injury to the brain (TBI) or spinal cord (tSCI). The objectives are to investigate if the intervention improves quality of life (QoL) and decreases burden. It is hypothesized that the family intervention improves problem-solving strategies and family dynamics, which will reduce the burden. This may improve the caregivers' mental health, which will improve the support to the survivor and QoL. Methods The study is an interventional, two-arm, randomized controlled trial. During a 2-year period, a total of 132 families will be included. Participants will be recruited from East-Denmark. Inclusion criteria are (1) TBI or tSCI, (2) >= 18 years of age, (3) >= 6 months to <= 2 years since discharge from hospital, (4) ability to understand and read Danish, (5) cognitive abilities that enable participation, and (6) a minimum of one family member actively involved in the survivor's life. Exclusion criteria are (1) active substance abuse, (2) aphasia, (3) prior neurologic or psychiatric diagnose, and (4) history of violence. Within each disease group, families will be allocated randomly to participate in an intervention or a control group with a ratio 1:1. The intervention groups receive the family intervention consisting of eight sessions of 90 min duration. Families in the control groups receive 2 h of psychoeducation. All participants complete questionnaires on QoL, self-perceived burden, family dynamics, problem-solving strategies, mental health, and resilience at pre-intervention, post-intervention, and 6-month follow up. Conclusion If the intervention is found to have effect, the study will contribute with novel knowledge on the use of a manual-based intervention including the entire family. This would be of clinical interest and would help families living with the consequences of TBI or tSCI.