People with mental illness (MI) are overrepresented in prisons, in part, because people with MI stay in prison longer. Correctional officers (COs) use discretion in force, violations, and segregation. Crisis intervention teams (CITs) are being used in corrections to reduce disparities in sanctioning and improve safety. This quasi-experimental, mixed-methods study includes 235 CIT COs who were surveyed before and after training on knowledge of MI, stigmatizing attitudes, and perception of response options. Non-CIT (n = 599) officers completed the same survey. Randomly selected CIT COs completed interviews 6 to 9 months following training (n = 17). CIT COs had significantly lower stigmatizing attitudes, more mental health knowledge, and better perceptions of options following CIT training compared with non-CIT COs. This preliminary work on CIT use in prison is promising; additional work is needed to determine whether these changes result in behavior change among COs and improvements in outcomes for people with MI.