This study examines the antecedents and outcomes of perceived similarity in mentoring relationships in a sample of 82 matched mentor-protégé dyads. Polynomial regression analyses were used to examine the association between actual and perceived similarity. Protégés were more likely to see themselves as similar to their mentors when they and their mentors shared either higher or lower levels of attachment security. However, sharing similar levels of relational self-construal was unrelated to protégés perceptions of similarity with their mentors. Path analyses revealed that protégés reported more organizational and professional commitment when they saw themselves as similar to their mentors, and that these associations were mediated by protégés’ reports of their mentors providing role modeling functions. These findings suggest that the effects of actual mentor-protégé similarity on perceptions of similarity may depend on the shared attribute, and provide further evidence of the importance of perceived similarity to not only mentoring relationships, but also to organizations.