This chapter examines the trajectory, challenges, and future directions of security cooperation between NATO and the Gulf Cooperation Council (GCC), focusing on the two decades since the launch of Istanbul Cooperation Initiative (ICI) in 2004. While the ICI provided opportunities for collaboration in areas such as defense reform, interoperability, counter-terrorism, and maritime security, it never developed into a full strategic partnership. Divergent assessments of regional threats, persistent divisions within the GCC, and NATO’s lack of a unified approach toward the Gulf constrained its effectiveness, bedeviling the initiative and leaving it without a strong guiding rationale. The chapter argues that shifting geopolitical dynamics, including the war in Ukraine, or renewed conflicts in the MENA, created new rationale for revisiting the cooperation. NATO’s redefined southern neighborhood strategy and the GCC states’ pursuit of greater strategic autonomy have reinvigorated dialogue and expanded avenues of multilateral engagement. While NATO is unlikely to act as a formal security guarantor in the Gulf, its function as a facilitator of capacity building in security sector and security coordination remains significant. The future of this relationship will depend on addressing political misalignments and fostering the sustained political will needed to institutionalize cooperation beyond technical initiatives and bilateral arrangements.