Background: The North Atlantic Treaty Organization (NATO) is the world’s largest and most powerful collective security organisation in modern times. Membership in this organisation is the objective and effort of many countries, including most of the countries of the Western Balkans. Membership ensures collective protection, security and political stability. Since its inception, NATO has emerged as a global force for security and the spread of peace almost across the globe. Not everyone deems it as such, considering the Russian Federation sees it as its main enemy. Its military operations have been centred around protecting human rights and maintaining peace. The best example of this commitment is NATO’s humanitarian intervention in Kosovo, one of the countries of the Western Balkans. Even after June 1999, NATO was present in this country and took care of the peace and security of the entire Western Balkans. The presence of this organisation in this part of the globe remained essential, as did knowing the geopolitical history of this region. The Balkans still suffers from nationalist policies and interethnic divisions, which in either case remain a very important factor for security in this region. One fundamental issue of Western Balkan countries is the acceleration of economic reforms, the rule of law and the fight against corruption to achieve membership in the European Union. Instead of these important issues in the Western Balkans, clashes have continued over border changes and nationalist rhetoric, which could undermine peace and security in this region. The current problems of the Western Balkans are inherited from the dissolution of the Socialist Federation of Yugoslavia. The wars in the former Yugoslavia, despite being the cause for the establishment of new independent states, did not fulfil the ethnic expectations of these countries. Given that the Republic of Serbia, in the preamble of the 2006 Constitution, foresees the Republic of Kosovo as its own territory,1 legal action that expresses territorial claims against a sovereign state poses a risk for new conflicts in the Balkans. A situation with conflicting tendencies is also present in the Republic of Bosnia and Herzegovina, where the official policy of the Serbian Republic of Bosnia has openly shown the tendencies for secession from the Federation and union with Serbia.2 This paper deals with the role that NATO has played and continues to play with its presence in the Balkans in maintaining peace and regional security, the challenges of security and building a stable peace in this region of Europe, where nationalist tendencies dominate as well as interethnic problems, lack of political culture and deficits of democracy. Methods: Combined scientific methods were used in this paper, starting with the qualitative method and literature review. The qualitative method was used to interpret the scientific theories related to security. Reviewing the literature, we managed to combine the results of other studies related to our study topic. This paper also used the analysis method, which helped us separate the elements from the totality of the study problem. The historical method has served to show the axis of the security problem in the Balkans and to explain the development of NATO. Results and conclusions: As a security organisation, during the Cold War, it served as a mechanism for collective defence against the nuclear threats of the Warsaw Pact and the spread of democratic values of the Western world. After the fall of the Iron Curtain, it has served as an organisation that promotes global peace and security, democracy, human rights and the rule of law. The existence of open political issues in the Western Balkans, in particular the territorial claims of Serbia against Kosovo, the nationalist tendencies of the Serbs from Bosnia and Herzegovina for separation from the Federation, the attempts of Russia to influence this region, using history, culture and intelligence services and some other issues such as the lack of political culture in Albania and Montenegro and the issues of North Macedonia with Bulgaria have posed risks to the regional security. In this geopolitical environment called the Western Balkans, the integration of all countries in NATO and its presence in this region is essential for the future and security. In this context, the membership of Kosovo and Bosnia and Herzegovina in NATO will have to be a priority for Western countries. The membership of these two states would serve regional peace and security.