This paper describes the NATO organisation and its significance in the Adriatic region. It presents the articles of the North Atlantic Treaty, which discuss collective defence and investments into one's own military forces. It also presents the influence of the organisation on the entire Adriatic region. The paper describes maritime capacities of Adriatic countries, the structure of their navy and the tasks of an individual authority. This is followed by a presentation of international operations performed under the auspices of the NATO organisation and the European Union, in which participated the Navy of the Republic of Slovenia.