Major changes in the world (e.g., wars, easy traveling, international economic relations) contribute to the fact that the integration of migrants into societies is considered an important challenge, especially for migration countries like Germany. Drawing on theories from social psychology, this chapter gives an overview over the research on successful integration and its obstacles. The chapter describes research on general group processes and migration, including stereotypes and prejudices as well as different theories on intergroup dynamics. We present an overview over major theories of acculturation research, followed by results on cultural learning and intercultural skills, as well as cultural dimensions and (types) of intercultural training. By presenting stress theory and cultural adaptation processes, it is further shown that migration may have a major impact on individual’s psychological states (e.g., culture shock). Lastly, different antecedents of intercultural success are outlined.