The article analyses the evolution, during the 2000s and 2010s, of civic engagement and political mobilization of post-Soviet Russian-speaking migrants living in the UK, and highlights the importance of these migrants' inherently transnational position in-between several polities. Transformations of their mobilizations are governed by: the changing context of immigration opportunities in the UK; the technological advancements of new modes of communication; larger political shifts in both Russia and the UK; and significantly, the availability of specific opportunity structures for mobilization. The principal opportunity structures available to these migrants in the 2000s fostered their mobilization as a culturally-defined minority migrant community and encouraged them to become part of a global network of Russian "compatriots". A new opportunity structure emerged in the early 2010s in the form of a transnational protest movement against political corruption in the Russian Federation. However, as the Russian government introduced policies effecting a growing disenfranchisement of Russians resident abroad from political developments in Russia itself, many Russians in the UK have started to look for new ways to engage. The politics of Brexit have become one new opportunity structure for them.