Multiculturalism in a European context increasingly has come to denote a concern with religious minorities. Claims for multicultural accommodation of minorities therefore potentially conflict with secularist requirements of separation of politics and religion. Whether there is a conflict depends on the general understandings of multiculturalism and secularism. The paper therefore distinguishes and examines different general understandings. Both multiculturalism and secularism can be understood as sets of policies, or as forms of minority accommodation or views about the relationship between religion and politics defined in relation to liberalism. Both understandings are problematic, so the paper proposes alternative formal understandings of multiculturalism and secularism. Multiculturalism denotes interpretations of what underlying (often liberal) principles imply under new circumstances of diversity. Secularism denotes what such principles imply for the relationship between politics and religion. Such formal understandings provide theoretical frameworks for specifying different conceptions of multiculturalism and secularism and for determining in precisely which respects conflicts might arise. But the frameworks also indicate that conflicts are not general or necessarily fundamental, and they provide tools for reinterpreting conceptions in ways that might avoid apparent conflicts.