The National Institute of Corrections urges use of motivational interviewing (MI) techniques by its workforce, and it is incumbent on criminal justice organizations to find effective methods of personnel training in this evidence-based practice. The current study evaluates impact of a 2-day, advanced MI workshop on personnel skills. Utilizing a validated skill instrument, four cohorts of juvenile justice personnel (aggregate N = 87) completed skill assessments at the outset and conclusion of an advanced MI workshop. Results indicated robust and reliable skill improvements across cohorts and skill domains, with nearly 80 percent of trainees attaining a proficiency criterion upon leaving the workshop. Furthermore, individual personnel with lesser reported education evidenced both lesser preworkshop skill and greater skill improvement such that postworkshop skills approximated more educated peers. Study findings reinforced the value of the professional training workshop as a practical and effective means of preparing personnel for monitored implementation of MI. (Published Abstract)