While much has been written about the politics of retrenchment, in a number of advanced industrial societies social policy expansion does occur today, which raises issues about how to study it in a post-retrenchment era. The present article explores the new politics of social policy expansion in Canada. Drawing on the work of Paul Pierson, we use an integrated framework that highlights the interaction of five factors: the availability of fiscal resources; the emergence of new social risks; the intensity and nature of partisan competition; the policy preferences of the main political parties; and the role of political institutions, especially federalism. Empirically, the article studies the politics of federal social policy expansion during the Harper (2006–2015) and Justin Trudeau (2015–) years, with a focus on three policy areas: child benefits (Universal Child Care Benefit and Canada Child Benefit), pensions (Old Age Security and Canada/Quebec Pension Plan) and Employment Insurance.