Abstract Background Studies investigating effectiveness of group psychotherapy intervention in sub-threshold depression have shown varying results with differing effect sizes. Aims A systematic review of randomised controlled trials of group psychotherapy in adults with sub-threshold depression has been conducted to present the best available evidence in relation to its effect on depressive symptomatology and prevention of incident major depression. Methods Electronic search for RCTs and a meta-analysis using random effects models to obtain a pooled estimate. Results Eight studies from six clinical trials met the inclusion criteria. Group psychotherapy is an effective intervention for reducing depressive symptoms in adults with sub-threshold depression in comparison to waiting list controls (MD = −3.48, 95% CI: −5.02, −1.93). The reported benefits for group intervention in reducing depressive symptoms in comparison to other active interventions did not reach statistical significance (MD = 0.37 95% CI: −1.29, 2.04). The benefit of group psychotherapy at follow-up is not maintained. Group psychotherapies do not appear to reduce the risk of incident depressive disorder during the follow up (RR = 1.15 95% CI: 0.85, 1.54). Dutch studies had bigger effect sizes than studies from other countries. The quality of reporting of all the studies was suboptimal. Conclusions The results of this meta-analysis show that group CBT interventions for patients with sub-threshold depression have a significant effect on depressive symptomatology at post treatment in both working age and older adult population. However it does not appear to reduce the incidence of major depressive disorders and has minimal or no effect on depressive symptomatology during follow-up.