This chapter explains the concept of neurodiversity and covers information on two neurodevelopmental disabilities: intellectual developmental disorder (ID) and autism spectrum disorder. This chapter also covers the history of these disabilities to familiarize readers with former diagnostic terms, as terminology, characteristics, diagnostic criteria, and prevalence in the population have changed considerably over the decades. Understanding the diagnostic information allows justice system practitioners to be better equipped to understand the characteristics of disabilities and implement accommodations and different communication strategies. The chapter concludes with information to clarify common misconceptions about autism and ID. Accurate knowledge of these conditions can assist practitioners in better communicating and working more effectively with individuals with disabilities.