Mixing tenures is now a widely accepted policy designed to tackle problems of social exclusion in disadvantaged neighbourhoods. However, the evidence base for mixing tenures is fragmented and ambiguous. With few exceptions, studies of mixed-tenure effects have been small, one-off investigations of individual communities, providing only a rudimentary basis for comparative evaluation. In attempting to address these issues, a national-level, ecological analysis of mixed tenure in Great Britain was conducted, using aggregate data from two decennial censuses and geocoded vital registrations. Asking the question whether mixing housing tenures is good for social well-being, the objective of the research is to establish under what, if any, circumstances tenure mixing is positively related to indicators of the social well-being of an area’s population. The findings provide little support for positive outcomes and lead the authors to question the efficacy of mixing tenures as a policy for improving social well-being.