Popular opposition to immigration is rooted in many factors. In this essay, we focus on one specific issue that has become prominent in recent debates—namely, the fear that the welfare state is being undermined by the impact of increasing ethnic and racial diversity. There are actually two concerns here: first, that ethnic and racial diversity as such makes it more difficult to sustain redistributive social policies because it is difficult to generate feelings of national solidarity and trust across ethnic and racial lines, and second, that the “multiculturalism” policies adopted to recognize or accommodate immigrant groups tend to further undermine national solidarity and trust. If either of these hypotheses were true, the very idea of a “multicultural welfare state,” a welfare state that respects and accommodates diversity, would be almost a contradiction in terms. We review the existing evidence and suggest that both hypotheses are overstated. The evidence to date suggests that there is no inherent tendency for either immigrant ethnic diversity or multiculturalism policies to erode the welfare state. We conclude with some speculation about the implications of this evidence for debates about the rights of noncitizens.