This short-term longitudinal study examined (a) adolescents' contact with mentors who share their background in relation to the importance they place on having such mentors, and (b) the associations of these perceptions with self-efficacy, identity, and commitment to a science career. Participants were 265 ethnically diverse adolescents (M age = 15.82) attending a 4-week science education program. Cluster analyses indicated that at Time 1, underrepresented ethnic minorities were more often in the cluster defined by feelings of importance of having a matched-background mentor but not having much contact. Perceptions of contact increased over time for these students and were associated with increased feelings of identity as a science student. The results suggest the need for attending to individual differences in students' preferences for matched-background mentors.