The two principles of the right to self-determination and the right of national sovereignty are the most fundamental principles governing the United Nations that are emphasized through various ways including the UN Charter (Articles 1(2), 2(1, 4, 7), 55(3), 73-74 and 77), UN covenants on human rights of 1966 and the Security Council’s resolutions (such as resolutions 1514 and 1803). Nevertheless, the conflict between the two principles has been erupted over time in a variety of situations in international arena. In the case of Kosovo, as an example, the parliament of Kosovo issued a unilateral declaration of the regional independence in an apparent conflict with the national sovereignty of former Yugoslavia; and the UN Security Council who had always highlighted, in its resolutions of 1169, 1199, 1239, 1244 and other documents released to solve the crisis between Yugoslavia and Kosovo, the need to respect the two principles in the form of recognizing Yugoslav national sovereignty and the right of Kosovan people to self-determination, did not in practice either prevent NATO military intervention in Yugoslavia or even condemn it and thus the Yugoslav national sovereignty eventually altered. Advisory vote of International Court of Justice on 22 July 2010 and the follow-up resolutions of General Assembly on 13 October 2010 approving the unilateral declaration of independence by Kosovo Parliament were all in support of Kosovo right of self-determination against the national sovereignty of Yugoslavia. Referring documents released and action taken by the UN and its other principle organs as well as other international entities to resolve the Kosovo crisis, this paper seeks to study the conflict between the two principles and analyze the situation in which one is preferred over the other.