<p>Amid the decline of the liberal international order, Europe’s regional security order (ERSO) is facing increasing destabilization driven by multiple internal and external shocks. Since the release of the first European Security Strategy in 2003, Europe’s security policy paradigm has undergone a distinct geopolitical shift. However, the outbreak and continuation of the Russia-Ukraine conflict reveal that this paradigm shift has not effectively addressed the severe challenges confronting ERSO. In this context, this study adopts the symbiotic theory developed by the Shanghai School to investigate the following: How can ERSO be understood through the lens of symbiotic theory? In what ways can symbiotic theory guide the transformation of the EU’s foreign and security policy paradigm? Using the Russia-Ukraine conflict as the primary case study, the research identifies crucial shortcomings in the EU’s current security policy across three dimensions: the security environment, security perceptions, and security instruments. The findings indicate that, despite a necessary return to military preparedness, the EU’s policy approach remains constrained by fragmented perceptions, geopolitical competition, and zero-sum logic, hindering the formation of an integrated and cooperative security order. Nevertheless, the symbiotic security order framework may provide a new approach for the EU to address these challenges.</p>