Mentoring has been shown to have a small to moderate effect on youth outcomes; however, implementation of research‐based practices improves program efficacy. Benchmark program practices and Standards in the Elements of Effective Practice for Mentoring (MENTOR, 2009) were assessed in the current study as predictors of match longevity. Secondary data analyses were conducted on a national agency information management database from 45 Big Brothers Big Sisters agencies and 29,708 matches from across the U.S. Agency leaders completed a web‐based survey describing their policies, procedures, and practices. Results revealed that the only individual Standard that was predictive of match length was the Training Standard. In addition, the sum total of both Benchmark program practices and Standards were associated with match length and long‐term relationships; however, neither predicted premature match closure. Results are discussed in terms of the importance of implementation of evidence‐based practices, particularly mentor training, for achieving effective mentoring outcomes.