Non-parent mentoring relationships are important protective factors for first-generation college students. Previous research has focused on singular mentoring relationships measured at one time point, failing to capture the breadth and dynamic nature of social networks. The current study is a longitudinal investigation of first-generation students' mentoring networks during their transition to college at a four-year, predominantly minority-serving commuter university. At the beginning and end of their first year, students (N = 176) responded to online surveys on their mentoring relationship(s), attitudes toward help-seeking, and college experiences. Cumulative support from pre-college mentoring relationships retained across the first year was positively associated with self-efficacy. Support from newly acquired mentoring relationships was positively associated with psychological sense of school membership. Network orientation was positively associated with self-efficacy and sense of school membership. These findings highlight the importance of diverse mentoring networks and demonstrate the utility of collecting longitudinal data on multiple mentoring relationships.