Illegal, Unreported, and Unregulated (IUU) fishing is the new global threat toward the sustainability of world’s fisheries and marine sectors. In 2009 Food and Agriculture Organizations (FAO) under United Nations established an agreement on port state measures which is intended to create a firm regulations to eliminate the practice of IUU fishing globally. However, as the coastal states which is experienced in the practice of IUU fishing, Indonesia is waited around seven years to finally ratify this agreement, although the impact from IUU fishing practices has been approached in several sectors. The objective of this research is to analyze the reasons behind Indonesian decision to ratify the PSMA by using several theoretical frameworks. That are concept of national interest, theory of foreign policy decision making process, and concept of international organizations. Based on the analysis that has been made, it resulted three important consideration which are used by Indonesia to support their decision in ratifying PSMA. These are the increase numbers of IUU fishing in Indonesian waters, the lack of Indonesian law enforcement about IUU fishing, and the need to overcome the practice of IUU fishing by cooperating in the global level.