The role of power, driving and shaping institutional change, is the central challenge in equity and sustainability governance reforms. Reforms aimed at fundamental change inherently question the status-quo, exposing who might win or lose with institutional change. As such, reform efforts are often met with various stabilizing mechanisms that oppose change, failing to meet their intended goals. While this has been consistently acknowledged by sustainability scholars, theory on institutional change has regularly ignored power, with a few exceptions. This dissertation aims at understanding the multi-directional relationship between power asymmetries among actors, governance processes, and their resulting institutional outputs and socio-ecological outcomes.To further this goal, the dissertation tackles three fronts: theory, case study development, and statistical testing. The driving research question focuses on power asymmetry among actors and how it shapes, and is shaped by, fundamental governance reforms aimed at achieving sustainability. It draws on theoretical foundations within common-pool resource governance, environmental justice, and social network theory, and combines qualitative and quantitative methods including traditional and systematic literature reviews, in-depth interviews, surveys, and network analysis. The analysis focuses on i) defining how power could be integrated into institutional analysis, ii) examining how asymmetries among actors shape institutional outputs, and iii) investigating the relationship between power asymmetries in reform processes and governance performance. Overall, this dissertation finds that power is not only key in defining governance processes, outputs, and outcomes, but it can also be quantitatively measured and integrated into institutional analysis.