The paper discusses the underpinnings, foundations and specific features of the Holy See's diplomacy, which has a spiritual and a secular component. The principle of the divine law represents a conditio sine qua non of the Holy See, and likewise the preservation of the Church's sovereignty. In the introductory part, the author gives a review of the beginnings of the Christianity and the emergence of the Papal Diplomacy, structure of the Holy See, the Roman Curia and the Vatican State. The contemporary agenda of the Holy See's diplomacy is introduced through the Vatican's views on contemporary subjects in the world, as well as through internal issues. Tradition versus progress, religion and technology, eternity as opposed to versatility, are some of the antagonistic relationships that are being considered within the paper. The concept of the soft power by Joseph S. Nye is explained through the Diplomacy of the Holy See and the relationship of the leading sovereign states with the sovereignty of the Church. Lastly, the author focuses attention to the sources of Croatian diplomatic tradition and the relationship between the Republic of Croatia and the Holy See. The conclusion is that the Christianity is deeply rooted in the history of Europe, thus denying of such identity can further deepen the crisis of the modern man on the European ground, however it is also necessary to implement the reform of the Church.