This study discusses the defense diplomacy carried out by Indonesia to South Korea for transfer of technology process in the development of KRI Alugoro-405 through out 2015-2019 period. In analyzing the case, the author uses the concept of defence diplomacy, transfer of technology and arms build up which has previously been motivated by bilateral cooperation between the two countries. This study uses a qualitative method with a descriptive type of research. Bilateral cooperation between the two countries had previously been established and agreed to increase to defense cooperation, especially in the procurement of submarines which began in 2011 until now. Cooperation with transfer of technology scheme is carried out to encourage the independence of Indonesian defense industry. The results of this study indicate that the defense diplomacy carried out by Indonesia is said to be successful and effective in the construction of KRI Alugoro 405 along with an increase in mutually beneficial partnership for both countries.