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Background Recent academic literature has shown a growing interest in the potential link between Autism Spectrum Disorder (ASD) and Functional Neurological Disorder (FND). A systematic literature review and meta-analysis was conducted to examine their co-occurrence.Method The review utilised a comprehensive literature search across various databases up to November 2024, using wide ranging sets of search terms, focusing on peer-reviewed original studies reporting the co-occurrence of ASD and FND. Twenty-four studies were eligible to be included.Results The study included 11,324 participants, predominantly female (73.4%). The meta-analysis estimated the proportion of ASD in FND populations to be 0.10 (95% CI: 0.07–0.15), with significant heterogeneity (I² = 97%, p < 0.01). Subgroup analysis highlighted variations between children and adults, as well as across specificr8 diagnoses. The proportion of ASD was 0.09 in adults and 0.10 in children with FND, 0.15 in adults and 0.19 in children with Functional Tic-Like Behaviours (FTLB), and 0.07 in children with Functional Seizures (FS).Conclusion Many studies have reported the co-occurrence of ASD in FND, suggesting a higher-than-expected rate of 10%. Emerging themes exploring the overlapping determinants of FND and ASD, are discussed. However, the significance of this correlation and the overlapping determinants that might explain it, require further research due to the heterogeneity in methodologies, settings, conditions studied and findings. Furthermore, the presence of publication bias warrants cautious interpretation of the results.