This paper aims to comprehend middle power’s foreign policy actions from an ideational perspective, specifically in regard to middle power identity and ontological security. Why do middle power choose to play a role of stabilizers and legitimizers of world order? While existing literature explains the motives behind middle powers’ foreign policies predominantly from material perspectives, this study sheds light on the impact of ideational factors on states’ foreign policy actions. Through case studies of Australia and South Korea, this research reveals that both countries perceive extensive structural changes as threats to their identity and seek to secure their ontological security by strengthening bilateral and multilateral ties with their strategic partners. In addition, the study finds that while the middle power identity of both countries significantly impact on their foreign policy decision-making, their perceptions of middle power identity differ. While Australia feels more empowered to influence and shape international order as a middle power, South Korea feels more responsibilities to fulfill its roles as a middle power. This evidence suggests that states’ actions cannot be solely explained by material factors, and that ideational factors play a significant role in shaping states’ foreign policy actions.