Regional security in South Asia is considered to be unstable and rapidly changing, with the Sino-Indian relationship being a particular focus of discussions. To date, aside from bilateral agreements, no clear programme to develop collective water management practices has been initiated among the Brahmaputra’s riparian countries. In the management of the Ganges–Brahmaputra–Meghna (GBM), neither India nor China is party to major global water norms, and they both remain keen to cope with water conflicts through bilateral foreign relations. This chapter aims to shed light on the nature, forms and outcomes of China’s diplomacy over the GBM. China’s diplomatic initiatives have revealed vested interests and that Beijing government is not only interested in seeking economic profits such as hydropower generation but also the domination of hydrological data and water policy information. There are both advantages and disadvantages to China’s diplomatic initiative to provide hydrological data to India. With the change of government, India has vested its own interests in such interactions. With complicated dynamics that have developed in Sino-Indian water disputes, China’s water diplomacy has not gained great success.