The impact of ethnic residential concentration on the process of integration of ethnic minorities into the mainstream society has been increasingly debated among both scholars and policy makers across Europe. This thesis seeks to contribute to this debate by addressing the effect of ethnic residential concentration on the political participation of Black Africans in Britain. The study pursues three main objectives: investigating the marginalising or mobilising impact of co-ethnic residential concentration on political participation; disentangling the processes underpinning this relationship by focusing on the effect of ethnic-based social networks, represented here by voluntary organisations, religious institutions and informal social networks; exploring the influence of the immigration-related heterogeneity that characterises the Black African community on the relationship between residential concentration, ethnic social networks and political participation. A mixed-method approach is adopted. The quantitative enquiry focuses on the Black African community as a whole and relies on secondary data drawn from the 2010 Ethnic Minority British Electoral Survey. The qualitative enquiry is based on primary data collected through face-to-face interviews and participant observation among Ghanaians and Somalis in London. The quantitative analysis shows that, among Black Africans, residential concentration has a mobilising effect on voter turnout but a marginalising effect on non-electoral participation. Ethnic social networks do not seem to mediate this relationship. Residential concentration is significantly, and positively, correlated to individual participation in ethnic places of worship and embeddedness in ethnic informal networks but not to involvement in ethnic organisations. In turn, the latter positively influences non-electoral engagement whereas ethnic places of worship and informal networks are not related to political engagement. The qualitative findings suggest that residential concentration is more relevant for the creation of and participation in ethnic organisations among Somalis than among Ghanaians. However, this relationship is likely to be influenced by other contextual factors such as institutional support, ethnic diversity and tribal homogeneity. Somali organisations also seem to play a more active political role than Ghanaian groups with regard to both electoral and non-electoral engagement. The two communities appear to be more similar when considering the relationship between ethnic religious institutions and informal connections with co-ethnics. These networks are not necessarily dependent on ethnic residential clustering and their effect on political engagement is primarily linked to informal political discussion. Overall, the results suggest that the relationship between residential concentration, ethnic social networks and political participation of Black Africans varies considerably between the two national groups researched, primarily due to their immigration-related characteristics, as well as across modes of political engagement (i.e. electoral, non-electoral) and local contexts.