Persons with mental disorders are overrepresented in the criminal justice system. Once involved in the criminal justice system, offenders with mental disorders are more likely to return to custody while on probation than their non-disordered counterparts, often for breaking the rules of community supervision. Risk assessments and risk management strategies employed by probation officers can lead to higher rates of returns to custody for probationers with mental disorders, and the current study is the first to examine these experimentally. Here, 234 probation officers provided risk assessments and risk management decisions based on a vignette portraying a probationer with a mental disorder, substance abuse disorder, both, or neither. Although substance abuse is a relatively stronger risk factor than a mental disorder, mental disorder had a stronger effect on officers’ risk assessments. In terms of risk management, mental disorders had the strongest effect on officers’ desire to manage risk with forced mental health treatment. These findings suggest that training for probation officers in the relative utility of mental disorder in predicting risk, in addition to evidence-based risk management strategies that take the focus off mental disorder, may improve outcomes for probationers with mental disorders.