During the first half of the 21st century, socioeconomic development is expected to contribute faster and to a greater extent to global water stress than climate change. Consequently, we aimed to identify conditions that can facilitate local adaptation planning for future water security, accounting for the socio-institutional context, developmental needs, and interests affecting water use and management. Our study focused on three forest landscapes in Latin America where water stress was identified as a current concern potentially leading to future social conflict if not addressed. In the three sites, we adopted a participatory approach to implement a systematic diagnostic framework for the analysis of socio-institutional barriers and opportunities influencing local adaptation decision making. This novel application enabled science-society engagement in which civil society organizations were coleading the research. The field methods we used involved participatory social network mapping, semistructured interviews, and validation workshops. Our study generated insights into several interventions that could help overcome barriers affecting the adaptation decision-making process, particularly in the diagnosis and early planning phases. Points of intervention included fostering local participation and dialogue to facilitate coproduction of knowledge, and strengthening the role of key central actors in the water governance networks. These key actors are currently bridging multiple interests, information sources, and governance levels, and thus, they could become agents of change that facilitate local adaptation processes. Working jointly with civil society to frame the research proved effective to increase awareness about water issues, which related not only to the technological, economic, and political aspects of water, but also to organizational processes. The involvement of civil society created genuine interest in building further capacity for climate adaptation and water security.