The adoption of risk assessment tools has increased in popularity in the juvenile justice system due, in part, to recommendations by the Juvenile Justice Delinquency Prevention Act (JJDPA). However, very little is known about whether adoption of these tools actually effectuates change in the way young offenders are handled. Qualitative and quantitative data were gathered from 111 juvenile probation officers (JPOs) from six probation offices before and twice after standardized, rigorous implementation of the Structured Assessment of Violence Risk for Youth (SAVRY) or the Youth Level of Service/Case Management Inventory (YLS/CMI). The purpose of this study was to examine JPOs' changes in attitudes and case management decisions following implementation of a risk/needs assessment (RNA) tool. There was a significant reduction in JPOs' perceptions of the proportion of young offenders who would reoffend. There were many shifts in JPOs' decision-making to be more consistent with Risk-Need-Responsivity practices, such as (a) making service referrals based on the fit between youths' criminogenic needs and services, and (b) assigning levels of supervision based on youths' level of risk. There was a shift in attention to more evidence-based dynamic risk factors. These changes occurred regardless of which RNA tool was used. Juvenile justice agencies are encouraged to adopt an evidence-based RNA tool using a sound implementation model in order to meet the objectives of the JJDPA and RNR practices. Benefits and barriers to adoption of RNA tools by juvenile probation departments are discussed.