Successful river basin governance is challenged by actor engagement in the various stages of planning and management. A governance approach for determining priorities for actors for sustainable management was developed, based on a river basin diagnostic framework consisting of four social-institutional and four biophysical indicators. It was applied in river basins in Australia, Brazil, China and France. Actors diagnosed current and target capacity for these indicators, and estimated synergistic influences of interacting indicators. The results reveal different priorities and transformative pathways to achieve basin plan outcomes, specific to each basin and actor groups. Priorities include biodiversity for the Murray-Darling, local water management needs for the São Francisco and Yellow rivers, and improved decision-making for the Adour-Garonne. This novel approach challenges entrenched views about key issues and actor engagement roles in co-implementation of the basin plan under existing prevailing governance models, with implications for engagement and international collaboration on basin governance.