This study evaluated the comorbidity rates of autism spectrum disorder (ASD) with functional neurological disorders (FNDs). A systematic review was conducted in accordance with Preferred Reporting Items for Systematic Reviews and Meta-Analyses guidelines. A subset of data was suitable for meta-analysis of proportions. Studies which assessed either the prevalence of ASD in patients with FNDs, or the prevalence of FNDs in patients with ASD were considered. Critical appraisal was conducted using Joanna Briggs Institute Critical Appraisal Tools. Fourteen studies met the inclusion criteria. Three cross-sectional studies which reported the comorbidity of ASD among children presenting with functional seizures met inclusion for meta-analysis. The pooled comorbidity rate of ASD in this group was 10.26% [3.92, 18.95], with an I2 value of 81%, indicating significant heterogeneity between studies. Most included studies (n = 5) reported on the rates of Somatic Symptom Disorders in adults with ASD. Comorbidity rates were also reported for ASD with Functional Motor Disorders and for mixed FND cohorts. Critical appraisal indicated that studies were underpowered, did not match cases with controls and failed to account for confounding factors. Identifying ASD and FND comorbidity may guide treatment options and reduce the risks of unnecessary medical investigations.