Two longitudinal studies considered the role of social identity factors in predicting well-being after students' transition to university. The transition (assessed before starting university and after 2 months at university) had a detrimental effect on well-being, but identification as a university student improved well-being. Both studies showed that the social context in which the change occurred either facilitated or hindered university identification. Specifically, perceived compatibility between old and new identities and having multiple group memberships (which were each influenced by social class background, Study 2) both increased likelihood of identification with the new group. These predictive relationships remained statistically reliable when controlling for other factors relevant to the transition. The results suggest that life transitions are difficult partly because they entail changes in group membership. Both studies also demonstrate that identification with a new group can help buffer individuals from the negative well-being consequences of change.