This study utilizes a social exchange perspective to examine mentors’ reported commitment and relational maintenance in formal youth mentoring relationships. One hundred and forty-five adult mentors from four mentoring programs completed surveys about aspects of their current youth mentoring relationship. Study measures assessed Investment Model variables (satisfaction, alternatives, investments, and commitment), stay/leave behavior, and reported use of relational maintenance strategies. Analyses supported hypotheses derived from the Investment Model, and commitment, in turn, predicted stay/leave behavior for mentors. In addition, a mediation model demonstrated that commitment mediates the relationships between some Investment Model variables and three of five relational maintenance strategies. The unique nature of formal youth mentoring relationships as prescribed is discussed, as are practical applications for mentoring programs.