Treatment of post-traumatic stress disorder (PTSD) in refugees and asylum seekers resettled in high-income countries presents specific challenges. This systematic review examined the effectiveness of psychosocial interventions for this group. We searched the Cochrane Central Register of randomised trials, CINAHL, EMBASE, PILOTS, PsycINFO, PubMed and Web of Science up to July 2016. Studies included randomised and controlled clinical trials comparing psychosocial interventions with waiting list or treatment as usual in adult refugees and asylum seekers with PTSD resettled in high-income countries. PTSD symptoms post-intervention was the primary outcome. We computed standardized mean differences (SMD) with 95% confidence intervals (CI). This study is registered with PROSPERO: CRD42015027843. Twelve studies were included in the meta-analysis. Psychosocial interventions were effective in decreasing PTSD symptoms relative to control groups (SMD -1·03, 95% CI -1·55 to -0·51; number needed to treat 4·4; I2 86%; 95% CI 77 to 91). Narrative exposure therapy, a manualized short-term variant of cognitive behavioural therapy with a trauma focus, was the best-supported intervention (5 RCTs, 187 participants, SMD -0·78, 95% CI -1·18 to -0·38, I2 37%; 95% CI 0 to 77). Methodological quality of the included studies was limited. Overall, psychosocial interventions for asylum seekers and refugees with PTSD resettled in high-income countries were found to provide significant benefits in reducing PTSD symptoms. Yet, the number of studies is small and their methodological quality limited, so that more rigorous trials should be conducted in the future.