The article examines the narratives of collective belonging among two migrant groups, Somalis and post‐enlargement Poles, who live in the London borough of Ealing (United Kingdom). In order to gain a better understanding of the processes of social identity formation, the article proposes a synthesis of a social identity approach, in particular the recent discursive developments in the field, with a political opportunity structure approach. Drawing upon these bodies of research, the article analyzes the understandings of collective identity among Somalis and post‐enlargement Poles according to three sets of social relationships: the group's relationship with the political environment; its relationship with other groups; and its relationship with people who share the same ascribed identity. The findings of the study confirm that social identity is shaped by not only intra‐ and intergroup cognitive elements but also by the political environment in which a group operates.