The relationship between mental illness, violence, and criminal behavior is complex, and involves a multifaceted interaction of biological, psychological, and social processes. In this article, we review the emerging research that examines the neurobiological and psychological factors that distinguish between persons with mental illness who do and who do not engage in crime and violence. Additionally, a novel model for understanding the interaction between mental illness and criminalness is proposed. (As defined by Morgan and colleagues, criminalness is defined as behavior that breaks laws and social conventions and/or violates the rights and wellbeing of others.) Stemming from this model and outlined research, we argue that management and treatment approaches should target the co-occurring domains of mental illness and criminalness to improve criminal and psychiatric outcomes. Specifically, we discuss and propose effective housing (management) and biopsychosocial intervention strategies for improving outcomes.