According to newswire reports, Laos agreed to delay the construction as other Mekong countries raised concerns about potential impacts downstream.
International development partners, including the Japanese government, will now be asked to assess the impact of planned dams on the Mekong.
The decision to delay the project was reached following a meeting between ministers from Cambodia, Thailand, Vietnam and Laos in Siem Reap, Cambodia.
The $3.8B dam is the first of 11 planned for the mainstream lower Mekong. Opponents of the project fear that, if given the go-ahead, the dam, and the others planned, could degrade the fragile ecology of the Mekong and negatively affect the lives of millions who depend on it for their livelihoods.