Refugees, asylum seekers, and internally displaced people experience a high burden of mental health problems owing to their experiencing traumas and stressful events. To summarise the available evidence and analyse the efficacy of brief psychological interventions (< 3 months) on improving mental health outcomes, including depression, anxiety, and post-traumatic stress disorder (PTSD)-related symptoms in refugees. We searched Medline, EMBASE, PsycINFO, CINAHL, and Global Index Medicus from inception to 19 December 2023. We included controlled studies using any cognitive behavioural therapy (CBT) or CBT-based therapies delivered over a short time (< 3 months), which reported mental health outcomes pre-and post-intervention. We conducted meta-analyses using random effects to derive pooled summary statistics. The quality of the evidence was assessed with the Cochrane Risk of Bias (RoB2) and ROBINS-I tools. This study is registered on the Open Science Framework, DOI 10.17605/OSF.IO/9CXU4. 34 eligible studies across 37 publications were retrieved for analysis, and 33 studies with 4479 participants were included in the meta-analysis. There was an overall improvement in immediate mental health outcomes for all three domains, with analysis of 13 studies on anxiety outcomes (SMD -1.12, 95% CI -1.72 to -0.52), 20 studies on depression (SMD -1.04, 95% CI -1.97 to -0.11), and 24 studies on PTSD (SMD -0.82, 95% CI -1.20 to -0.45). At 3 to 6-month follow-up, however, analysis of mental health outcomes shows no significant change from baseline, with a SMD of 0.24 (95% CI -0.94 to 1.42) across 4 studies, -0.73 (95% CI -2.14 to 0.68) across 9 studies, and 0.29 (95% CI -0.94 to 1.53) across 12 studies for anxiety, depression, and PTSD respectively. Low-quality evidence shows brief psychological interventions have a positive immediate effect on refugees and internally displaced people's mental well-being. However, these effects do not persist in the short-term follow up. Heterogeneity was high, even among subgroups, impacting our findings' generalisability.