Purpose: Peer mentoring programs in higher education settings support incoming students in their transition and adaptation to college life. Mentoring program evaluation research primarily focuses on student outcomes and documents mentoring relationship quality (MRQ) as an important component of programs that facilitate change. The current study examines MRQ in a college peer mentoring program and explores its association with mentors' and mentees' perceptions of family relationships. Design/methodology/approach: The sample included 629 first-year students (M[subscript age] = 18.4 and 54.2% female) and 88 mentors (M[subscript age] = 20.6 and 65.9% female). Each mentor was matched with eight to 10 incoming students in the same department. Dyadic data were collected prior to the program (pre-test) and at the end of the fall semester (mid-program) and spring semester (post-test). At pre-test assessment, mentors and mentees rated their family relationships, perceived trust, loyalty, and fairness in their families. At follow-up assessments, mentees reported their MRQ, mentoring duration, and mentoring activities. Findings: A multilevel modeling analysis revealed that mentees' and mentors' perceptions of loyalty in their families predicted higher levels of MRQ at the end of the program. However, mentors' perceived trust in their families was negatively associated with MRQ. Originality/value: This study adds to the youth mentoring literature by focusing on family-of-origin experiences of both mentors and mentees from a dyadic and relational perspective. These findings have implications for future research and the practice of formal mentoring programs in college settings.