IntroductionChronic pain and disability are now well-recognised long-term complications of blunt chest wall trauma. Limited research exists regarding therapeutic interventions that can be used to address these complications. A recent feasibility study was completed testing the methods of a definitive trial. This protocol describes the proposed definitive trial, the aim of which is to investigate the impact of an early exercise programme on chronic pain and disability in patients with blunt chest wall trauma.Methods/analysisThis mixed-methods, multicentre, parallel randomised controlled trial will run in four hospitals in Wales and one in England over 12-month recruitment period. Patients will be randomised to either the control group (routine physiotherapy input) or the intervention group (routine physiotherapy input plus a simple exercise programme completed individually by the patient). Baseline measurements including completion of two surveys (Brief Pain Inventory and EuroQol 5-dimensions, 5-Levels) will be obtained on initial assessment. These measures and a client services receipt inventory will be repeated at 3-month postinjury. Analysis of outcomes will focus on rate and severity of chronic pain and disability, cost-effectiveness and acceptability of the programme by patients and clinicians. Qualitative feedback regarding acceptability will be obtained through patient and clinician focus groups.Ethics/disseminationLondon Riverside Research Ethics Committee (Reference number: 21/LO/0782) and the Health Research Authority granted approval for the trial in December 2021. Patient recruitment will commence in February 2022. Planned dissemination is through publication in a peer-reviewed Emergency Medicine Journal, presentation at appropriate conferences and to stakeholders at professional meetings.Trial registration numberISRCTN65829737; Pre-results.