Introduction: Despite recent efforts to understand the possible impact of contextual factors on adolescents' involvement in ethnic bullying, most existing studies have focused on the effects of one context at a time. As adolescents are simultaneously exposed to the influence of multiple socialization agents, the aim of this study was to investigate whether teachers' and classmates' tolerance towards ethnic minorities could buffer the effect of perceived parental prejudice on adolescents' involvement in ethnic bullying. Methods: Data were collected between January and February 2020 from 9th grade adolescents (N = 582; M[subscript age] = 15.23; SD = 0.65; 50.9% female; 30.7% with an immigrant background), and their teachers (N = 72; aged between 27 and 65 years; 79% female), belonging to 37 classrooms located in Italy. Results: A cross-sectional multilevel analysis showed that teachers' tolerance moderated the effect of perceived parental prejudice on adolescents' involvement in ethnic bullying. Specifically, we found that in classrooms with low levels of teachers' tolerance, perceived parental prejudice was significantly associated with students' involvement in ethnic bullying. Conversely, in classrooms with high levels of teachers' tolerance, parental prejudice was no longer associated with ethnic bullying. Furthermore, classmates' tolerance was not significantly associated with students' involvement in ethnic bullying and did not moderate the association between perceived parental prejudice and adolescents' engagement in ethnic bullying. Conclusions: Findings are discussed highlighting the important role of school as a context to promote positive multicultural relations and the unique role played by teachers in affecting adolescents' behaviors.