Background: Previous studies and national reports have all noted that a significant proportion of the young people who display harmful sexual behaviours have intellectual disabilities. However, research on the topic has been scarce. This study presents a systematic review of the literature relating to clinical instruments specifically developed or adapted for adolescents with intellectual disabilities who display harmful sexual behaviours. Method: An electronic search of databases was completed for published articles in English from the earliest possible date to the end of 2013. Results: No published articles met the full search criteria. This confirmed the lack of published clinical measures, apart from two risk assessment instruments. Conclusions: Given the lack of measures, it is recommended that the focus of future research needs to be on developing or adapting instruments that will offer researchers' and clinicians' empirical as well as clinical data on this all-too-often-overlooked population of vulnerable youth.