The importance of ethnicity/race for adolescents’ identity (i.e., centrality), and how that importance changes over time, may in part be a function of the social contexts that they inhabit. Although centrality has shown to be an adaptive component of ethnic/racial identity, little is known about how centrality changes during adolescence in relation to these social contexts. The current study examined the role of same-ethnic/racial peers and friends in the longitudinal development of ethnic/racial identity centrality. Drawing on four waves of data over 2 years collected with a diverse sample of 350 adolescents (Mage at W1 = 15.2; 69 % female), the findings indicated that when adolescents had a greater proportion of same-ethnic/racial friends, they reported feeling that their ethnic/racial identity was more central to their sense of self six months later. However, this effect was strongest among adolescents with a low proportion of same-ethnic/racial peers in school, and weakest among adolescents with a high proportion of same-ethnic/racial peers in school. The implications of these findings for our understanding of the joint effects of peer and friend diversity in relation to ethnic/racial identity are discussed.