With the rapid growth of industrialization, Hanoi is facing the threats from water pollution. It affects not only heath problem but also regional development negatively.
This paper focuses on the possibility of local government as an agent to implement international cooperation bringing out effectiveness and spread effects, and analyzes the case of the cooperation between the local government of Chiba‐prefecture in Japan and Hanoi in Vietnam. By examining the case study, this paper aims to show that the international cooperation between local governments has effectiveness and spread effects in the environmental improvement, and clarify the key factor of such effect.