PURPOSE: Mindfulness- and acceptance-based interventions (MABIs) are receiving increasing attention in the treatment of mental disorders. These interventions might be beneficial for patients with anxiety disorders, but no prior reviews have comprehensively investigated the effects of this family of interventions on clinical samples. The aim of this study was to review and synthesize extant research on MABIs for patients with diagnoses of anxiety disorders. METHODS: We conducted a systematic search of relevant databases according to pre-defined criteria. Studies were eligible for inclusion if they employed MABIs for patients diagnosed with anxiety disorders. RESULTS: Nineteen eligible studies were found. Meta-analysis of within-group pre- to post-treatment effects yielded overall Hedges'g effect sizes of 1.08 for anxiety symptoms and 0.85 for depression symptoms. For controlled studies, overall between-group Hedges'g was 0.83 for anxiety symptoms and 0.72 for depression symptoms. Moderator analyses examined whether intervention type, design, treatment dosage, or patient sample was associated with systematic variation in effect sizes. No significant moderating effects were found on the variables examined, apart from an observed superiority in effect size for clinical trials on samples of patients with mixed anxiety disorders. However, differential effect sizes indicated benefits of adding specific psychotherapeutic content to mindfulness training, as well as an advantage of individual over group treatment. CONCLUSIONS: MABIs are associated with robust and substantial reductions in symptoms of anxiety and comorbid depressive symptoms. More research is needed to determine the efficacy of MABIs relative to current treatments of choice, and to clarify the contribution of processes of mindfulness and acceptance to observed outcome.