Abstract: Background: Exposure to potentially morally injurious events is increasingly recognised as a concern across a range of occupational groups, including UK military veterans. Moral injury-related mental health difficulties can be challenging for clinicians to treat and there is currently no validated treatment available for UK veterans. We developed Restore and Rebuild (R&R) as a treatment for UK veterans struggling with moral injury-related mental health difficulties. This trial aims to examine whether it is feasible to conduct a pilot randomised controlled trial (RCT) of R&R treatment compared with a treatment-as-usual (TAU) control group. Methods: We will use a feasibility single-blind, single-site RCT design. The target population will be UK military veterans with moral injury-related mental health difficulties. We will recruit N=46 veteran patients who will be randomly allocated to R&R (n=23) or TAU (n=23). Patients randomised to R&R will receive the 20-session one-to-one treatment, delivered online. Veterans allocated to TAU, as there are currently no manualised treatments for moral injury-related mental health problems available, will receive the one-to-one treatment (online) typically provided to veterans who enter the mental health service for moral injury-related mental health difficulties. We will collect outcome measures of moral injury, post-traumatic stress disorder (PTSD), alcohol misuse, common mental disorders and trauma memory at pretreatment baseline (before randomisation), end of treatment, 12 weeks and 24 weeks post-treatment. The primary outcome will be the proportion of patients who screen positive for PTSD and moral injury-related distress post-treatment. Ethics and dissemination: This trial will establish whether R&R is feasible, well-tolerated and beneficial treatment for veterans with moral injury-related mental health difficulties. If so, the results of the trial will be widely disseminated and R&R may improve access to effective care for those who struggle following moral injury and reduce the associated negative consequences for veterans, their families and wider society.