Background: Sleep disturbances are often referred to as a hallmark and as core symptoms of post-traumatic stress disorder (PTSD). Untreated sleep disturbances can contribute to the maintenance and exacerbation of PTSD symptoms, which may diminish treatment response and constitute a risk factor for poor treatment outcome. Controlled trials on treatment of sleep disturbances in refugees suffering from PTSD are scarce. The present study aims to examine sleep-enhancing treatment in refugees with PTSD. We aim to assess if add-on treatment with mianserin and/or Imagery Rehearsal Therapy (IRT) to treatment as usual (TAU) for PTSD improves sleep disturbances. We will study the relation between sleep disturbances, PTSD symptoms, psychosocial functioning and quality of life. Methods: The study is a randomised controlled superiority trial with a 2 × 2 factorial design. The study will include 230 trauma-affected refugees. The patients are randomised into four groups. All four groups receive TAU - an interdisciplinary treatment approach covering a period of 6-8 months with pharmacological treatment, physiotherapy, psychoeducation and manual-based cognitive behavioural therapy within a framework of weekly sessions with a physician, physiotherapist or psychologist. One group receives solely TAU, serving as a control group, while the three remaining groups are active-treatment groups receiving add-on treatment with either mianserin, IRT or a combination of both. Treatment outcome is evaluated using self-administered rating scales, observer ratings and actigraph measurements at baseline, during treatment and post treatment. The primary outcome is subjective sleep quality using the Pittsburgh Sleep Quality Index. Secondary outcome measures are objective sleep length, nightmares, PTSD severity, symptoms of depression and anxiety, pain, quality of life and psychosocial functioning. Discussion: This trial will be the first randomised controlled trial to examine sleep-enhancing treatment in trauma-affected refugees, as well as the first trial to investigate the effect of IRT and mianserin in this population. Therefore, this trial may optimise treatment recommendations for sleep disturbances in trauma-affected refugees. Based on our findings, we expect to discuss the effect of treatment, focussing on sleep disturbances. Furthermore, the results will provide new information regarding the association between sleep disturbances, PTSD symptoms, psychosocial functioning and quality of life in trauma-affected refugees. Trial registration: EudraCT registration under the name 'Treatment of sleep disturbances in trauma-affected refugees - a randomised controlled trial', registration number: 2015-004153-40 , registered on 13 November 2015. ClinicalTrials.gov, ID: NCT02761161. Registered on 27 April 2016.