Autism spectrum disorder (ASD) is characterized by neurodevelopmental differences in the brain that manifest in divergent social and communicative abilities and stereotyped behaviours. The prevalence of ASD diagnoses has risen sharply in recent years, possibly due to changes in diagnostics criteria, but this does not fully explain the increase. ASD has known genetic predispositions, but vulnerability factors, such as influences from the external environment, are thought to influence the development of the condition. Exposure to pesticides has been of interest here, as both human and rodent studies have demonstrated links between certain pesticides and ASD-like behaviours and diagnosis. This systematic review sought to summarize current knowledge from preclinical and epidemiological studies. It included 45 human and 16 preclinical studies from animal models, focusing on Organophosphates, Organochlorine, Pyrethroid, Neonicotinoid, Carbamate, and exposure to mixed pesticides. The anayisis yielded no clear conclusion as the complexity of influencing factors made the studies hard to summarize. I.e. different types of pesticides, exposure duration, exposure routes and methodologies used in the various studies. Another problem highlighted by the author is that it is impossible to look at pesticide exposure in isolation as it always co-exists with other factors that may be harmful or beneficial for the development of the nervous system. Such as lifestyle, socioeconomics, educational status, ethnicity, gender or genetics. However, evidence suggests that some compounds like Organophosphates, Organochlorine and Pyrethroid appear to have an impact on cognitive and behavioural functions in children following exposure. Yet, further clinical research is needed to draw firm conclusions on pesticide exposures in humans and ASD in general. Overall this review yields a comprehensive overview of various pesticides and their evidence on ASD. Whilst awaiting further research more solid conclusions may be drawn by focusing on specific compounds and their existing research