Acceptance and commitment therapy (ACT) is a third-wave cognitive behavioral therapy that has shown promise as an effective treatment for reducing trauma-related symptoms. Although there have been systematic reviews on the clinical effectiveness of ACT for posttraumatic stress disorder, there are no known meta-analyses published on the impact of ACT in adult populations with trauma-related symptoms. Hence, the purpose of this meta-analysis and systematic review was to update the literature and assess the effectiveness of ACT interventions for decreasing trauma-related distress in adults who have developed trauma symptoms following exposure to one or more traumatic events. A systematic review of the literature was completed, and between-groups random effects meta-analysis was conducted assessing trauma symptom reduction at the initial posttest. Subgroup analyses were also performed to assess differences between groups based on research design, type of trauma, and comparator group. A meta-analysis of 11 studies revealed a moderate and statistically significant overall effect of ACT on symptom reduction at immediate posttest (Hedges' g = -.423, 95% CI [-.605, -.240]; I² = 25.75%), indicating that on average, those who received ACT interventions reported fewer trauma symptoms postintervention than those in various comparison groups. Ultimately, this research provides additional evidence supporting the effectiveness of ACT interventions for clients reporting trauma-related concerns. (PsycInfo Database Record (c) 2024 APA, all rights reserved).