The European Pillar of Social Rights (EPSR) sits at the fulcrum of EU social policy-making. As a formally non-binding interinstitutional proclamation composed of 20 social rights and principles, its (potential) effects are far from clear. Through a comprehensive empirical study, this thesis explores the effects of the EPSR on policy instruments advancing social rights at EU level. The main argument is that the EPSR has a remarkably active effect on EU social policy-making since its adoption in 2017, which results from the use of the initiative by actors in the EU interested in advancing more social protection, inter alia the European Commission’s Directorate General for Employment, Social Affairs and Inclusion and the European Parliament’s Committee on Employment and Social Affairs. This finding is complemented by three other key findings. Political actors intentionally drafted elements of the EPSR to strengthen the initiative’s legal and political authority. This in turn contributed to the potential justiciability of the EPSR: the Court of Justice could use the initiative in its case law giving it legal effect. The findings also demonstrate the importance of social actors in policy-making. The thesis builds on an interdisciplinary approach combining legal and political science research methods. It uses an actor-centred theory, building on sociological and constructivist insights. It adds new insights to three strands of scholarship: it provides a comprehensive understanding of EU social policy-making, adds an important case to the study of EU soft law, and has broader methodological and substantive relevance for the study of European integration.