This article presents results from a 3-year longitudinal study of the growth patterns and correlates of perceived discrimination by adults and by peers among Black, Latino, and Asian American high school students. Results revealed a linear increase over time in levels of perceived discrimination by adults, whereas perceptions of discrimination by peers remained stable over time. Asian American and non-Puerto Rican Latino adolescents (primarily Dominican) reported higher levels of peer and/or adult discrimination than did Puerto Rican youth, whereas Black adolescents reported a steeper increase over time in levels of perceived discrimination by peers and by adults than did Puerto Rican adolescents. Peer and adult discrimination was significantly associated with decreased self-esteem and increased depressive symptoms over time. Ethnic identity and ethnicity were found to moderate the relationships between perceived discrimination and changes in psychological well-being over time. Results underscore the need to include perceptions of discrimination when studying the development and well-being of ethnic minority adolescents.