The past 30 years have witnessed a dramatic change in the way Western democracies deal with ethnic minorities. In the past, ethnic diversity was often seen as a threat to political stability, and minorities were subject to a range of policies intended to assimilate or marginalize them. Today, many Western democracies have adopted a more accommodating approach. This is reflected in the widespread adoption of multiculturalism policies for immigrant groups, the acceptance of territorial autonomy and language rights for national minorities, and the recognition of land claims and self-government rights for indigenous peoples. We refer to these policies as 'multiculturalism policies' or MCPs. The adoption of MCPs has been controversial, for two reasons. The first is a philosophical critique, which argues that MCPs are inherently inconsistent with basic liberal-democratic principles. Since the mid-1990s, however, this philosophical debate has been supplemented by a second argument: namely, that MCPs make it more difficult to sustain a robust Welfare State (hereafter WS). Critics worry that such policies erode the interpersonal trust, social solidarity and political coalitions that sustain a strongly redistributive WS. This paper reviews the reasons why critics believe that MCPs weaken political support for redistribution, and then examines empirically whether the adoption of MCPs has, in fact, been associated with erosion of the WS. This examination involves two steps: we develop a taxonomy of MCPs and classify Western democracies as 'strong', 'modest' or 'weak' in their level of MCPs. We then examine whether the strength of MCPs is associated with the erosion of the WS during the 1980s and 1990s. The evolution of the WS is measured through change in four indicators: social spending as a percentage of GDP; the redistributive impact of taxes and transfers; levels of child poverty; and the level of income inequality. We find no evidence of a consistent relationship between the adoption of MCPs and the erosion of the WS. Our analysis has limits, and we hope it stimulates further research. Nevertheless, the preliminary evidence presented here is clear: the case advanced by critics of MCPs is not supported. The growing ethnic diversity of Western societies has generated pressures for the construction of new and more inclusive forms of citizenship and national identity. The evidence in this paper suggests that debates over the appropriateness of multiculturalism policies as one response to this diversity should not be preempted by unsupported fears about their impact on the WS.