Social sciences have experienced the return of institutions into the main research agenda, and a new institutionalism has been developed to understand the role of institutions. The award of the 2009 Nobel Prize in Economics to the political scientist Elinor Ostrom for her “analysis of economic governance, especially the commons” has promoted the recognition of modern institutional analysis and resized contemporary political economy. This paper is an integral approach to Ostrom’s contributions and analyzes the evolution of her thinking throughout the major advances of her work over time. Her early contributions on public policy and polycentric systems, her seminal study on social norms in the governance of the commons, the focus on social capital and her multi-level framework of socio-ecological systems are her main contributions on polycentric governance.