Whilst the political rhetoric of social mix has been similar across countries, asymmetries in their housing and planning systems and institutions owing to dissimilar underlying values, norms, and cultures has defined national and municipal practices of implementation. The purpose of this paper, based on a literature review and semi-structured interviews with government, local officials, and academics, is twofold. First, to investigate why and how city planners in the municipality of Copenhagen have used strategies of social mix in the fields of housing and land-use planning, and how these policies have evolved to deal with recurrent shortages of affordable housing. Second, to highlight the contingent nature of social mix and argue the need for more context and more sensitive analysis of social mix policies and practices. Whilst many have claimed that social mixing is a euphemism for gentrification, this paper argues that the concept can contribute to a more progressive housing and urban planning agenda.