African regimes commonly use strategies of balanced ethnic representation to build support. Decentralisation reforms, often promoted in order to improve political representation and state access, can undermine such strategies. In this article we use the example of the DR Congo to show the extent to which the multiplication of decentralised provinces is upending a political system largely based until now upon collective ethnic representation in the state. Not only are Congo's new provinces more ethnically homogeneous than their predecessors, but many of them have also witnessed political takeover and monopolisation by the province's dominant ethnic group. In addition, the increased number of Congolese who now find themselves non-autochthonous to their province of residence heightens their vulnerability and the potential for local conflict. Decentralisation, whose intent was proximity to governance, might well end up excluding more Congolese from the benefits of political representation. The article uses original empirical evidence on provincial ethnic distributions to support its claims.