This study examined the role of participation in a year‐long school‐based group mentoring program, Project Arrive (PA), on increasing resilience during the first year of high school among students identified as being at high risk for school dropout. Participants were 114, ninth grade students taking part in one of 32 PA mentoring groups, and 71 statistically matched comparison students (53% male, 75% eligible for free/reduced‐price lunch, 62% Latinx). Using a propensity score with inverse probability of treatment weighting (IPTW) to reduce selection bias, and a multi‐level model to account for non‐independence of data within mentoring groups, we examined changes from pre‐test to program exit on seven external resilience resources (developmental supports and opportunities) and four internal resilience assets (personal strengths). At program exit, PA participants had higher adjusted means than comparisons on six external resources, including school support, school belonging, school meaningful participation, peer caring relationships, prosocial peers, and home meaningful participation. PA participants also had higher adjusted means on one internal asset, problem solving. Results point to the promise of group mentoring as an approach for increasing resilience among academically vulnerable adolescents.