Individuals with neurodevelopmental disorders (NDDs) who become involved in the mental health or criminal justice systems due to sexually inappropriate behaviors can present unique challenges to clinicians with regards to assessment and treatment approaches. This chapter focuses on individuals with autism spectrum disorder (ASD) and intellectual developmental disorder (intellectual disability or ID) who engage in sexually inappropriate or sexual offending behavior. The chapter covers the evolution of diagnostic terminology, prevalence rates, risk assessment tools, evidence-based treatment, treatment frameworks, several case studies, and concludes with recommendations for assessment and treatment.