The purpose of the interdisciplinary Companion Modelling (ComMod) approach in renewable resource management is to facilitate collective learning, negotiation, and institutional innovation about concrete problems faced by rural communities. The objective of this communication is to present and to compare the effects of the ComMod approach on collective water management at three different pilot sites located in upper northern Thailand (two sites) and west-central Bhutan. At these sites, water management is a cross-cutting problem: the processes of agricultural commercialization and increased pressure on the land led to the need for stakeholders to agree on new rules for the management of limited water resources. In the Lingmuteychu watershed of Bhutan, water sharing at rice transplanting has been a perpetual issue, without a way forward, while in montane northern Thailand a looming water scarcity is linked to the increased demand from expanding irrigated horticultural cropping systems. The paper compares the way this approach was flexibly adapted and implemented at the three sites according to the local contexts. The main effects of the ComMod process at the three sites are then presented according to a common framework analysing the processes of collective learning, negotiation, and coordinated action that were stimulated. It emphasizes the following effects: learning about the current situation and awareness of a problem to be solved collectively, understanding each other's perceptions and common agreement on the nature of the problem, exploration of new management rules to solve the problem, and concrete implementation of institutional innovation. The discussion focuses on the factors contributing to, or limiting, the achievement of institutional innovation. The role of the local institutional context and the possibility to establish inter-institutional dialogue among multiple levels of organization is highlighted. Finally, we point out the need for specific monito