Metacognitive training (MCT) is a new, widely used intervention for psychosis. The present meta-analysis examines the efficacy of MCT in schizophrenia. Fifteen studies comparing effects of MCT on positive symptoms, delusions or acceptance of MCT with a control group were included in this meta-analysis. These studies comprised a total of 408 patients in the MCT condition and 399 in the control condition. The moderating effects of masking of outcome assessment, randomization, incomplete outcome data, use of an active control intervention, and individual vs group MCT were investigated. Possible effects of sensitivity analyses and publication bias were also examined. The results show a significant overall effect of MCT for positive symptoms (g = -0.34, 95% CI [-0.53, -0.15]), delusions (g = -0.41, 95% CI [-0.74, -0.07]) and acceptance of the intervention (g = -0.84, 95% CI [-1.37, -0.31]). Using only studies being at low risk for bias regarding randomization, masking and incomplete outcome data reduced effect sizes for positive symptoms and delusions (g = -0.28, 95% CI [-0.50, -0.06] and g = -0.18, 95% CI [-0.43, 0.06]), respectively. This meta-analysis demonstrates that MCT exerts a small to moderate effect on delusions and positive symptoms and a large effect on acceptance of the intervention. The effect on delusions is reduced, but remains significant when potential biases are considered