Background The increased recognition of psychiatric and behavioural disorder in adults with autism spectrum disorder (ASD) has been associated with more frequent use of psychopharmacologic intervention in this population. However, limited evidence supports the effectiveness of these interventions for adults with ASD. Objective To review and synthesise the evidence regarding the effectiveness of psychotropic medication in reducing behavioural disturbance in adults with ASD. Data sources and study selection Electronic literature search of PubMed plus manual reference checks of all articles on psychopharmacology in adults with ASD published in the English language between 1985 and 2015. Results and conclusions A total of 43 studies were included in the analysis. The results indicate that only two medications, fluoxetine and risperidone, can be considered as promising evidence-based practices for adults with ASD. Given the rising prevalence of ASD, along with increased use of psychopharmacologic intervention in this population, there is a clear need for methodologically rigorous research to establish the effectiveness of these interventions. The subsequent establishment of clinical guidelines for medication use in this population is essential.