This research report provides a summary of the key findings from a rapid evidence assessment of mentoring research, to examine the impact of these programmes on re-offending. The results provide some promising evidence on the effectiveness of mentoring on reducing re-offending; however this was largely driven by the studies of lower methodological quality. Mentoring was found to be more effective in smaller scale studies in reducing re-offending when mentors met with their mentee frequently, and had a greater effect the more time was spent during each meeting, as well as when mentoring was combined with other interventions. The vast majority of the studies included in the review were from the U.S. which further limits the generalisability of the findings to this country.