Metacognition refers to cognitions about our own cognitions. In recent years, there has been a concerted effort to examine metacognition among autistic people. The results from these studies have produced a mixed picture, with some concluding that autistic people are just as accurate as typically developing people in judging their own cognitions and others providing evidence of reduced accuracy. The aim of this meta-analysis is to amalgamate this research to obtain a clearer picture of the evidence to date. A total of 17 studies comparing 412 individuals diagnosed with autism and 453 typically developing individuals were included in the meta-analysis. The data revealed a moderate, but heterogeneous, reduction in metacognitive accuracy among autistic individuals in comparison with non-autistic individuals. A critical review of the results suggested that, despite the overall reduction in metacognitive accuracy, performance was not universally diminished among autistic participants across studies. Accuracy may be undiminished on certain types of metacognitive task. Moreover, across all tasks, there was moderate difference in metacognitive accuracy between autistic and non-autistic children, but only a small difference in metacognitive accuracy between autistic and non-autistic adults.