Urban governance systems need to be adaptive to deal with emerging uncertainties and pressures, including those related to climate change. Realising adaptive urban governance systems requires attention to institutions, and in particular, processes of institutional innovation. Interestingly, understanding of how institutional innovation and change occurs remains a key conceptual weakness in urban climate change governance. This paper explores how institutional innovation in urban climate change governance can be conceptualised and analysed. We develop a heuristic involving three levels: (1) “visible” changes in institutional arrangements, (2) changes in underlying “rules-in-use”, and (3) the relationship to broader “governance dilemmas”. We then explore the utility of this heuristic through an exploratory case study of urban water governance in Santiago, Chile. The approach presented opens up novel possibilities for studying institutional innovation and evaluating changes in governance systems. The paper contributes to debates on innovation and its effects in urban governance, particularly under climate change.