Abstract The goals of Crisis Intervention Team (CIT) programs include improving safety during encounters between police and persons with mental illnesses, diverting persons with mental illnesses away from the criminal justice system, and increasing referral and access to mental health services. CIT is a systemic intervention, and as such, its implementation and effectiveness are influenced by existing practices and infrastructures. However, little research has considered the context in which CIT programs are implemented. In this paper, we present research on CIT in four Chicago police districts that vary in terms of two contextual factors hypothesized to influence the impact of CIT training on how calls involving persons with mental illnesses are resolved. Using data from 112 patrol officers in four Chicago police districts, we consider the impact of mental health services availability and CIT saturation (the percentage of district personnel that are CIT certified). Findings indicate that CIT training increased direction to mental health services primarily in districts with greater availability of mental health services. In districts with low service availability, higher CIT saturation increased direction to mental services. The opposite pattern emerged for contact only or informal call resolution. No effects were found for arrest as a call outcome.