Growing empirical research finds that a correctional system devoted to punishment is ineffective and can produce criminogenic effects. As a result, justice organizations, including probation, are encouraging managers and staff to adopt evidence-based practices (EBPs), supported by scientific evidence, such as validated risk and needs assessments and cognitive-behavioral therapies. Implementation of EBPs falls heavily on street-level workers, such as probation officers (POs) as they implement policy, yet little attention examines whether and how EBPs align within the traditionally authoritarian justice environment. Using over 1,000 hr of observation and interview data with probation staff, the present study examines how probation staff understand and use EBPs. Findings indicate that probation staff continue to make discretionary decisions regarding whom they can use EBPs with and situations in which EBP use is appropriate. Findings have significant implications for the acceptability, feasibility, and transportability of EBPs in criminal justice environments.