The study of intergroup attitudes, particularly in terms of prejudice, has a long history within social psychology. However, the way intergroup attitudes have been conceptualized and measured has evolved in significant ways. Moreover, beyond documenting the role of attitudes in intergroup relations, there is a much deeper understanding of factors that moderate this relationship. In this chapter, we review research on the origins of prejudicial intergroup attitudes in a range of basic psychological processes, individual differences, social relations, and socio-structural factors. We then examine common distinctions between subtle or indirect expressions of intergroup attitudes and their blatant expression, as well as between explicit and implicit prejudice, and we explain how these distinctions have stimulated methodological development in the measurement of intergroup attitudes. We also consider ongoing and emerging debates on the role of intergroup attitudes in predicting discriminatory behavior. Following that, drawing on our review of basic processes that shape intergroup attitudes (e.g., personal experience, social categorization, and social influence), we focus on efforts to improve intergroup attitudes and intergroup relations. We conclude by highlighting new avenues for future work in the study of intergroup attitudes and its role in the dynamics and outcomes of intergroup relations.