Media depictions of autism have the potential to have either positive or detrimental impacts on the lives of autistic people. This systematic review aimed to examine (1) the accuracy and authenticity of fictional media portrayals of autism (Part A) and (2) the impact of viewing such portrayals on knowledge about autism and attitudes towards autistic people (Part B). Seventeen articles met the inclusion criteria and were included in the review: 14 for Part A and 3 for Part B, comprising five experimental studies. The media reviewed in Part A covered a 30-year period (1988–2017). Several stereotypical and unhelpful portrayals surfaced. Positive portrayals of autism highlighted strengths and reflected nuance. Overall, participants in the fiction conditions in Part B were significantly more likely to attribute positive traits to an autistic person than those in the control conditions, with medium effect sizes ranging from 0.57 to 0.73. There were no improvements in knowledge. Given the small number of studies included in this review, further evidence is needed to understand the conditions under which fictional media may be effective. There is also a need to develop measures that accurately and respectfully measure autistic people’s experiences of community knowledge and attitudes. Lay abstract The way autism is represented in fictional media can impact people’s views of autistic people. For example, representations may contribute to negative views of autistic people as being unusual or dangerous, or they may challenge stereotypes and instead highlight the strengths of autistic people. This work aimed to review previous research to understand how autistic people have been represented in fictional media (Part A). It also sought to understand whether viewing fictional portrayals of autism has an impact on people’s knowledge of autism and attitudes towards autistic people (Part B). Of 14 studies that were included in Part A, several unhelpful and stereotypical portrayals of autism emerged. Positive portrayals were those that highlighted the strengths of autistic people and reflected nuance. There is a need for greater diversity in representation of autism in fictional media. For example, not all autistic people are white heterosexual males. Across the five studies included in Part B, there were no improvements in people’s knowledge of autism after watching or reading a short segment from a fictional TV series or novel that depicts an autistic person. Although there was a significant improvement in people’s attitudes towards autistic people, these findings do not provide a complete picture given the short length of the media exposure and small number of studies. Future studies should investigate how multiple exposures to the representation of autistic people in both fictional and non-fictional sources can affect people’s understanding of autism. There is also a need to develop more accurate and respectful ways of measuring people’s knowledge of, and attitudes towards, autism.