To extend research on fundamental motivational orientations into a new domain, we explored the achievement (positive) and avoidance (negative) orientations of formal organization-based mentors and proteges as joint predictors of personal learning experienced by both parties. We also examined the extent of mentoring functions provided by mentors as a hypothesized partial mediator. Regression analyses of 8-month data from 61 dyads revealed that mentors' personal learning was predicted by proteges' achievement (positive) and avoidance (negative) orientations, whereas proteges' personal learning was predicted by their own achievement orientation (positive). Although the extent of mentoring functions facilitated personal learning equally among mentors and proteges, it did not function as a mediator. Finally, mentor-protege congruence on achievement orientation had implications for the personal learning of proteges.