With the continuous evolution of globalization and international affairs, the role of non-state actors in international relations has become increasingly prominent. This article explores the question of whether states have the right to exercise self-defense against non-state actors. It argues that the international law does not explicitly rule out the possibility of states exercising the right of self-defense against non-state actors in the face of armed attacks. It also points out that although the “Unwilling or Unable” test maintains delicate balance between safeguarding the national security of the victim state and respecting the sovereignty of the territorial state where the non-state actors are located, this doctrine lacks theoretical support and has not gained opinio juris internationally. Therefore, the exercise of the right of self-defense still needs to adhere to the principles of “necessity” and “proportionality”. This implies that states have the right to take necessary actions, including the right of self-defense, to safeguard their national security when facing armed attacks from non-state actors. Moreover, countries must deepen communication and cooperation in international and regional affairs, uphold the international order underpinned by international law, and ensure that the exercise of self-defense aligns with the common interests of the international community and the objectives of international peace and security.