To examine the unique functions of same- and cross-ethnic friendships, Latino (n = 536) and African American (n = 396) sixth-grade students (M[subscript age] = 11.5 years) were recruited from 66 classrooms in 10 middle schools that varied in ethnic diversity. Participants reported on the number of same- and cross-ethnic friends, perceived vulnerability, friendship quality, and the private regard dimension of ethnic identity. Whereas same-ethnic friendships were uniquely associated with stronger private regard, more ethnic diversity and cross-ethnic friendships were uniquely associated with less perceived vulnerability. Multilevel structural equation modeling tested whether cross-ethnic friendships mediated the diversity-vulnerability relation. Although cross-ethnic friendships did not significantly mediate this relation at the classroom level, these friendships predicted less vulnerability at the individual student level.