This study aims to explain the enhancement of cooperation between Indonesia and Melanesia Spearhead Group Countries. MSG countries are countries in the closest South Pacific region to Eastern Indonesia. This region is the most dependent region in the world. It is proved by their dependence on foreign aid. The relationship between Indonesia and the Melanesian region was not good before 1983. Then the relationship between the two increased time by time and rapidly raised in 2015-2017. This study uses qualitative methods that try to construct reality understanding why did the cooperation increase. The Collective Identity by Alexander Wendt is used as the relevant theory to explain changes that affect the relationship of two sides. The main reason why cooperation has increased is that because Indonesia and the MSG Countries have a mutual need, they are the same as archipelago countries and Melanesian ethnicity. These reasons cause Indonesia and MSG Countries to increase cooperation. Keywords: Indonesia, Collective Identity, Melanesian, MSG, South Pacific