The western coastal sea of the Gulf of Tonkin is adjacent to Chinese marine area, and its catchment is concerned the territory of some Southeast countries. The transboundary environmental problems consist of pollution from river source (Red River, Ca River and Ma river etc.), pollution from air circulation, pollution through marine currents in the Gulf of Tonkin (oil spill and marine litter), transposition of hazardous wastes, old ship dismantlement and hazardous exotic organism... Up to now, there has been a weak interest in the transboundary environmental problems in Vietnam generally and the western coastal sea of the Gulf of Tonkin. For preventing and mitigating their impacts to marine environment, ecosystem and population health, it is necessary to raise the awareness of community, enforce regulations and policy, and apply advanced science, technology, management, and stre.ngthen the international cooperation.