This paper aims to examine the Tseng-Wen Reservoir Trans-basin Water Diversion Project from the perspective of environmental justice, and to explore the disputes on the distribution of interests and environmental risks of the project, and the policy implications of local action. It reveals the multiple perspectives of stakeholders on the project, the various knowledge claims among experts of different disciplines, and conflicts between local knowledge and the experts. The authorities have framed the project as either a water supply effectiveness issue or an economic development issue. However, environmental groups fear that the project involves extensive self-interest and bribery, consider the experts’ thinking on water resource development to be limited, and are of the opinion that local aboriginal tribes suffer disproportionate environmental risks. It highlights the problem of a lack of recognition of people and place. The tribes’ unique cultural meanings, invisible cultural assets, and their integrated relationship with nature are excluded from the EIA report, which lacks fully informed consent or substantial participation from local residents in the decisionmaking process. The project involves scientific controversy as well as unpredictable and irreversible impacts on the environment which cannot rely upon experts and technocracy only. It needs to recognize local particularities, and lay knowledge needs to be included in knowledge production and policy-making. This paper argues for the need for early involvement and public deliberation on water resource planning, for consensus seeking through continuous intercultural and interdisciplinary dialogue, and for alliance building to bring transformation.