We are facing socio-ecological crises and failing to meet the basic needs of everyone in society whilst living within planetary boundaries. These interconnected problems are complex, which require urgent transdisciplinary efforts informed by theories of change. How can we address this in cities in a way that is equitable and sustainable, since cities are complex, dynamic ecosystems with interdependent relationships? What processes, dynamics and determinants are involved? What and how are local policies designed and implemented with the intention of achieving sustainable wellbeing for all? How do normative competences shape cities' capacities to directly respond to social and ecological needs? How can we effectively assess and compare advancements being made in different cities? Given this complexity, more systemic, integrated, and theoretical understanding is needed. We present a new conceptual framework which aims to strengthen understanding of the processes, dimensions, determinants, bi-directional relations and dynamics that influence the opportunities for cities to become more equitable and sustainable. The framework places a specific emphasis on political determinants, and can serve as a tool to guide public policy design and evaluation, and monitoring of the progress made across the various dimensions of sustainability wellbeing for all in different urban contexts.