The Mekong River Basin (MRB) is a trans-boundary river shared by six countries. The governance by the Mekong River Commission (MRC) of the Lower Mekong Basin (LMB) is weak. This study investigates the welfare effects in the year 2030 arising from strengthening the MRC's governance versus joint management of the entire MRB. Without joint management, strengthening the MRC's governance has a huge potential to achieve welfare gains and it requires that the interests of all stakeholders be equally balanced. A bargaining approach shows that the LMB has no incentive to negotiate with China and is better off strengthening the MRC's governance instead. If such strengthening could be realized, further welfare gains of joint management by a wider and stronger MRC, including China, would be very small.