The Cumulative Impact Assessment and Management of Renewable Energy Development in the Sekong River Basin, Lao People’s Democratic Republic aims to support decision making for sustainable development of renewable energy resources. In the past, private sector interests have largely directed developments in the basin on a first-come, first-served basis. The findings of the CIA indicate the need for a Sekong Basin power development master plan incorporating renewable energy (hydropower, solar, and wind) and thermal power. There is an opportunity to establish the trajectory of future development based on a strategic assessment of local and regional power demand and with consideration of the range of potential uses of natural resources in the basin. This approach would result in greater investment efficiency, a close match between power production and demand, and more opportunities to address adverse impacts through the full range of options available in the mitigation hierarchy.