A shift towards sustainable urban water management is widely advocated but poorly understood. There is a growing body of literature claiming that social learning is of high importance in restructuring conventional systems. In particular, governance experimentation, which explicitly aims for social learning, has been suggested as an approach for enabling the translation of sustainability ideas into practice. This type of experimentation requires a very different dynamic within societal relations and necessitates a changed role for professionals engaged in such a process. This empirically focused paper investigates a contemporary governance experiment, the Cooks River Sustainability Initiative, and determines its outcome in terms of enabling social learning for attaining sustainable water practice in an urban catchment. Drawing on the qualitative insights of the actors directly involved in this novel process, this paper provides evidence of changes in individual and collective understanding generated through diverse forms of social interaction. Furthermore, the research reveals perceived key-factors that foster and/or hamper the execution of this new form of experimentation, including project complexity, resource intensity and leadership. Overall, this paper highlights that, while implementation of governance experimentation in a conventional setting can be highly challenging, it can also be highly rewarding in terms of learning.