Developmental theory suggests that a well-developed ethnic identity serves as a secure position which allows people to be more open and accepting to people from other ethnic groups. To examine this prediction, two studies were carried out. In Study 1, 713 college freshmen from four ethnic groups were surveyed regarding positive attitudes toward other groups and were assigned to ethnic identity statuses on the basis of scores on the Multigroup Ethnic Identity Measure (Phinney, 1992). The results showed that Asian American and Latino students with an achieved ethnic identity reported significantly more positive attitudes toward other groups than did those in ethnic identity diffusion. Study 2 used qualitative methods with 124 adolescents from five ethnic groups. Ethnic identity and intergroup attitudes were assessed with open-ended questions regarding views of one's own ethnicity and experiences with other ethnic groups. Results showed that ethnic identity achieved adolescents, compared to diffuse adolescents, gave responses indicating greater awareness and understanding of intergroup relations. Overall, the results provide evidence that a secure ethnic identity is associated with positive intergroup attitudes and mature intercultural thinking. (Contains 6 tables.)