Many Western societies are becoming increasingly ethnically diverse. In this chapter, we focus on whether diversity at a macro level (that is, diversity of individuals’ social contexts) is beneficial or disadvantageous for intergroup relations. We therefore review research in political and social psychology on the consequences of macro-diversity for majority members of the host societies, looking at social trust, intergroup attitudes, and political behaviour as the main outcome variables. First, we start by conceptualising macro-level diversity and outlining some methodological considerations. Next, we briefly review the evidence on the question whether ethnic diversity has positive or negative consequences for intergroup relations. We then focus on two potential psychological mechanisms explaining effects of increased macro-diversity on individual outcomes: perception of threat versus intergroup contact. Moreover, we discuss individual and contextual moderators of the relation between ethnic diversity and intergroup attitudes. Finally, we end this chapter by outlining future directions for research.