How people come to develop a feeling of belongingness to a new social group and orchestrate this new group membership with pre-existing identities within the self-concept is a theoretically and socially relevant phenomenon that has received increased scientific attention in recent years. Models from different fields of psychology – including social, cultural, and organizational psychology – have proposed factors involved in this change and integration process along with consequences of this phenomenon. We present overview of this literature, including a recent model on the process of identity integration: the cognitive-developmental model of social identity integration. Specifically, this model highlights the fundamental cognitive and developmental processes involved as people develop new social identifications and integrate their different identities into their overall self-concept. We then present recent empirical evidence testing the model. Finally, we propose conceptual, methodological, and statistical avenues for future research on identity change and integration.