Autism Spectrum Disorder (ASD), previously known as Pervasive Development Disorder (PDD) is a developmental disorder present from early childhood. Children diagnosed with ASD commonly exhibit symptoms of ADHD resulting in increased severity of symptoms and impairment of functioning. This group of children is frequently treated with methylphenidate which has been recommended by some but criticised by others. This systematic review aims to explore the effect of methylphenidate treatment on symptoms of ASD, functioning and adverse effects  Six articles were extracted from five different databases (Medline, Psych INFO, PubMed, Scopus, and Web of Science) and chosen based on a pre-determined inclusion and exclusion criteria. The results show that MPH treatment may be successful as an intervention for some children with ASD showing ADHD symptoms while other children are very susceptible to adverse effects with some being unable to tolerate the treatment. The chosen studies provided limited acknowledgement of the effect on functioning making it an important focus for future research. It is important that professionals are aware of the negative effects MPH might cause to ensure a positive outcome and well-being for children with this disorder. There is a need for further understanding of the connection between ASD and ADHD with additional exploration of possible moderators such as IQ, dose size and level of functioning.