The China-led Lancang-Mekong Cooperation (LMC) mechanism, which had its first leaders’ summit in March 2016, may sound boring but has big implications for water governance in the Mekong region, and for dividing ASEAN states in their dealings with China. In this commentary for the ‘Reporting ASEAN’ series, Johanna Son says that  the Beijing-dominated forum that is far from neutral for smaller states. LMC could also undercut the ASEAN centrality the organisation so values.