Immigration remains one of the most important political and social issues in contemporary society, with immigration-related diversity posing significant challenges to democratic nations. While much of the existing research addresses macro- and meso-level factors related to immigrant integration, we contend that the field would benefit from a more explicit integration of social psychology frameworks. These frameworks underpin many of these dynamics but are often neglected. This chapter reviews the application of social psychological concepts, theories, and processes to immigration studies at the micro, meso, and macro level, both in the US and Europe. We explore how individuals, institutions, and state policies respond to immigration and, conversely, how these responses impact intergroup relations, identity formation, stigmatization, well-being, and the overall integration of immigrants. The chapter concludes with a discussion of potential avenues for future research.