Using social cognitive career theory as a theoretical foundation, we examined the relationship between mentor and protege organizational socialization as well as the mediating role of career, psychosocial, and role-modeling support received by proteges. We also examined the moderating role of mentorship formality in the relationship between mentor socialization and the receipt of career, psychosocial, and role-modeling support. Using survey data collected from 209 ongoing mentoring dyads from five banks in Taiwan, regression results indicated that mentor socialization was positively related to career functions and role modeling that proteges received, as well as protege socialization. Career support partially mediated the relationship between mentor socialization and protege socialization. Mentorship formality moderated the relationship between mentor socialization and psychosocial support, suggesting that the positive relationship between mentor socialization and psychosocial functions only bears out in informal mentoring relationships. We offer a discussion of the theoretical and practical implications of these findings.