This meta-analytic review examines the efficacy of mindfulness-based therapy (MBT) in reducing anxiety and mood symptoms in clinical populations. The study identified 39 studies with a total of 1,140 participants, including those with cancer, generalized anxiety disorder, depression, and other psychiatric or medical conditions. The results suggest that MBT is moderately effective for improving anxiety (Hedges’ g = 0.63) and mood symptoms (Hedges’ g = 0.59) from pre to post-treatment. In patients with anxiety and mood disorders, MBT was associated with larger effect sizes (Hedges’ g = 0.97 for anxiety and Hedges’ g = 0.95 for mood symptoms). These effects were robust and maintained over follow-up. The review also found that MBT was effective for reducing symptoms in chronic medical conditions, such as cancer. The findings support the use of MBT as a promising intervention for treating anxiety and mood problems in clinical populations.This meta-analytic review examines the efficacy of mindfulness-based therapy (MBT) in reducing anxiety and mood symptoms in clinical populations. The study identified 39 studies with a total of 1,140 participants, including those with cancer, generalized anxiety disorder, depression, and other psychiatric or medical conditions. The results suggest that MBT is moderately effective for improving anxiety (Hedges’ g = 0.63) and mood symptoms (Hedges’ g = 0.59) from pre to post-treatment. In patients with anxiety and mood disorders, MBT was associated with larger effect sizes (Hedges’ g = 0.97 for anxiety and Hedges’ g = 0.95 for mood symptoms). These effects were robust and maintained over follow-up. The review also found that MBT was effective for reducing symptoms in chronic medical conditions, such as cancer. The findings support the use of MBT as a promising intervention for treating anxiety and mood problems in clinical populations.