© 2014 Elsevier B.V. Background Generalized anxiety disorder (GAD) is a common and highly comorbid anxiety disorder characterized by repetitive negative thinking (RNT). Treatment trials tend to exclude individuals with non-primary GAD, despite this being a common presentation in real world clinics. RNT is also associated with multiple emotional disorders, suggesting that it should be targeted regardless of the primary disorder. This study evaluated the acceptability and effectiveness of brief group metacognitive therapy (MCT) for primary or non-primary GAD within a community clinic. Methods Patients referred to a specialist community clinic attended six, two-hour weekly sessions plus a one-month follow-up (N=52). Measures of metacognitive beliefs, RNT, symptoms, positive and negative affect, and quality of life were completed at the first, last, and follow-up sessions. Results Attrition was low and large intent-to-treat effects were observed on most outcomes, particularly for negative metacognitive beliefs and RNT. Treatment gains increased further to follow-up. Benchmarking comparisons demonstrated that outcomes compared favorably to longer disorder-specific protocols for primary GAD. Limitations No control group or independent assessment of protocol adherence. Conclusions Brief metacognitive therapy is an acceptable and powerful treatment for patients with primary or non-primary GAD.