This report evaluates the New York City-based Arches Transformative Mentoring program, finding that participation in the program reduces one-year felony reconviction by over two-thirds, and reduces two-year felony reconviction by over half, with especially profound impacts for the youngest program participants. The program's evidence-based curriculum is completed over a 6-12-month period and delivered in a group setting by "credible messengers," direct service professionals with backgrounds similar to the populations they serve. The evaluation recommends continuing and even growing the Arches program by tailoring the curriculum to align with participant experiences, providing more mentor training, offering opportunities for full-time employment, and expanding the program's length, alumni engagement, and age range.