Delusional disorders within a criminological context are often overlooked, misunderstood or simply dismissed as behavioural characteristics that do not belong within the field of criminology. However, case studies show that there is a need to understand how delusional disorders could lead to the committing of crime. To address this need a historical overview of delusional disorders is presented. Thereafter, the five criteria and seven subtypes of delusional disorders, as defined by the APA/DSM-IV-TR (2000), are discussed to provide a better understanding of these disorders. Five of the seven subtypes are also contextualised within the South African legal framework. Although the APA/DSM-IV-TR (2000) offers a comprehensive definition of these disorders, the limitations of the definition are discussed as well as types of delusional disorders that are not included in the definition. The aim is to explain the importance of delusional disorders within the field of criminology in the context of the APA/DSM-IV-TR (2000). Actual case studies and elements of particular crimes are used to highlight the relationship between delusional disorders and crime. Furthermore, the challenge related to criminal liability and determining whether individuals can be held accountable for their deluded actions, is discussed. Recommendations on how to treat and prevent potentially dangerous individuals from committing crimes while acting under these delusions are also dealt with.