The 2030 Agenda and Sustainable Development Goals (SDGs) have put very high emphasis on water security for all, leaving no one behind. A key target for achieving SDG 6 on water security is 6.5, which aims to implement integrated water resources management at all levels by 2030, including through transboundary cooperation as appropriate. In order to achieve water security SDG 6 and related targets, groundwater has to play an important role as it is the primary source of drinking water worldwide with over one third of world population depending entirely on groundwater as well as it is crucial for food security as 43% of the total water used for irrigation comes from groundwater. Before the 2030 Agenda, the United Nations General Assembly through resolution A/C.6/68/L.25,2013 commended to the attention of Governments the draft articles on the law of transboundary aquifers for bilateral or regional agreements and arrangements for the proper management of transboundary aquifers. UNESCO’s International Hydrological Program has been actively following UNGA resolution as well as contributing to SDG Target 6.5.2 with UNECE on mapping and management of transboundary groundwater aquifers by formalising operational arrangements. The operational arrangements consist of treaty, convention, agreement or other formal arrangement as well as joint bodies for transboundary water cooperation promoting annual exchange of data and information, which can lead to adoption of coordinated water management plans or joint objectives. This presentation will highlight the challenges and opportunities for transboundary groundwater cooperation globally and in Asia and the Pacific region through existing and new mechanisms.