The subject of this research is the security policy of Finland in the context of membership in the European Union. Because of its specific geopolitical position, Finland has faced major security challenges in preserving its national sovereignty and integrity since acquisition its independence, which has contributed to the development of its security policy as a very important factor in pursuing its national interests. Aware of its geopolitical position and instructed by its historical experience and the conflict with the Soviet Union, Finland during the Cold War started a new policy towards its largest neighbors known as the Paasikivi-Kekkonen line. The basic doctrine of a such policy during the Cold War period was to avoid conflicts of great powers, to develop good neighbourly relations, to contribute to the strengthening of international institutions and to advocate for world peace. With the end of the Cold War, Finland decided to join the European Union. As a member of the Union, Finland supports the strengthening of the common security and defence policy, participates in operations led by the United Nations, the Organization for Security and Cooperation in Europe, the European Union or other international organizations or groups of countries, supports the development of regional security cooperation through NORDEFCO, and in line with the objectives of the Partnership for Peace, Finland actively cooperates with NATO in peace support operations.