Although literature provides strong evidence for the beneficial role of outgroup contact, longitudinal knowledge regarding the formation and change of outgroup contact remains improvable. Using a longitudinal, large-scale data set including 6,726 majority and minority participants (M[subscript age] = 14.98 years at Wave 1; 55% female) from 4 western European countries that were followed in 3 waves over 2 years, we systematically examined the development of outgroup contact during adolescence and tested the role of hypothesized predictors (i.e., intergroup attitudes and social identity) for explaining this development. In the majority, growth curve models revealed consistent patterns of ethnic homophily characterized by a continuous decline of outgroup contact, whereas this negative growth was buffered by a positive change of intergroup attitudes and a negative change of national identity during adolescence. In contrast, in the minority, outgroup contact was characterized by higher mean levels and a nonlinear development (i.e., no systematic decline or increase) of outgroup contact. Findings highlight the developmental importance of adolescence for promoting positive intergroup relations, especially for the majority, and emphasize the usefulness of contact interventions with adolescent students in school.