This article aims at assessing the Northeast Asia Peace and Cooperation Initiative (NAPCI) from the perspective of middle power diplomacy. The NAPCI has a mid-level form with emphasis on routine processes, and its scope is discrete in that it is limited to soft-security issues. Its intensity tends to be accommodative rather than combative, while its target focuses on regional cooperation. As a catalyst, Korea proposed the NAPCI and mobilized supporters in international community. As a facilitator, she hosted the Northeast Asia Peace and Cooperation Forum and successfully regularized it, even if sacrificing agenda-setting powers and institution-building roles as a manager. The Korean government must establish a like-minded coalition with existing regional institutions, MIKTA, and international (non-governmental) organizations. Also, the discourse of trust needs to be diffused through widespread networking with global civil society.