The effects of school and classroom racial/ethnic diversity on peer victimization, self-blame, and perceived school safety were examined in a racially/ethnically diverse sample of students followed over the three years of middle school. Sixth grade students (N = 5,991, 52% female; M = 11.63 years) were recruited from 26 urban middle schools that systematically varied in racial/ethnic diversity. Based on student self-report, the sample was 31.6% Latino/Mexican, 19.6% White, 17.4%, Multiethnic/Biracial, 13% East/Southeast Asian, 10.9% Black, and 6.9% Other very small racial/ethnic groups. Each school had a structural diversity score based on the number and size of racial/ethnic groups enrolled. Using a novel method based on course schedules and class rosters, each student’s individual exposure to diversity in their classes was assessed to capture dynamic diversity. Latent growth modeling showed that structural school diversity and dynamic classroom diversity were both related to less victimization at the start of middle school and a decrease over time. Dynamic classroom diversity buffered the associations between victimization and self-blame and between victimization and perceiving school as unsafe. Dynamic classroom diversity was more protective than structural school diversity. Implications for practice, intervention and policies to promote school racial/ethnic diversity were discussed.