The article is devoted to the study of the prerequisites and procedural aspects of the conclusion of the Act of Unity of the Ukrainian People’s Republic and the Western Ukrainian People’s Republic on January 22, 1919, which was the culmination of centuries-old efforts of Ukrainians to unite their historical national lands within the boundaries of a single sovereign and independent state of Ukraine. The process of affirming the unity of the Ukrainian lands historically began with the search for support for the Western Ukrainian People’s Republic among the political elites of Trans-Dnieper Ukraine. The pre-accession agreement concluded between representatives of the Western Ukrainian political elite and the newly formed Directorate of the Ukrainian People’s Republic provided for the procedure for ratifying the union of the two parts of Ukraine. The aspirations of Western Ukrainian People’s Republic representatives regarding equal representation in the highest bodies of state administration, which they previously discussed with the Management, were not realized. In fact, the Directory recognizes the autonomous status of Western Ukrainian People’s Republic as one of the regions of Ukraine under the name Western Region of the Ukrainian People’s Republic. The management of the Directory was aware of the declarative nature of the connection. The paradigm of the historical perspective and parallels through the centuries brings us back to the need to constantly study the strengths and positive experiences of the past, study mistakes in order to avoid them in the future. The period of Ukrainian national development studied in the article went through many difficult trials, but this encouraged Ukrainians to raise national liberation ideas to a new level - awareness of the need for national and territorial unity. The leaders of the Ukrainian People’s Republic and Western Ukrainian People’s Republic failed to realize the positive aspirations that were laid down in their positive movement towards the unity of the state. The main drawback was that the main institutions of power of the Ukrainian People’s Republic remained formed according to the imperial model. There was a lack of professional and at the same time nationally conscious personnel. An important historical experience of the relationship between the two parts of Ukraine, which must be taken into account in the current conditions of Ukraine, is the development of a common national policy, the vector of which is national interests, sovereignty and protection of the independence and territorial integrity of the state.