The article explores the history of archival work in Belarus starting with September 17, 1939, when the Red Army units crossed the SovietPolish border and entered Western Belarus, until the end of World War II. Three time periods are set: September 17, 1939 – June 22, 1941; June 22, 1941 – Autumn of 1943; Autumn of 1943 – Autumn of 1945, each of which has its own characteristics regarding the state of archival work in the republic. The author notes the positive influence of the reunification of the State Archival Funds (SAF) of Belarus and the completion of the formation of the archival institutions’ network system through the inclusion into it of the state archives, created in five new regions of Western Belarus. At the same time, the author brings on display the facts of the destruction of the Second Rzeczpospolita former administrative institutions’ archives, their removal from the places of origin. The article emphasizes the important role of the specialists with archival education from Russia in streamlining and organizing the work of archives on the territory of Western Belarus. After June 22, 1941, the Belarusian archives found themselves in a difficult situation: about one percent of the total volume of the State Archival Funds of the republic was evacuated to the East. The only fully evacuated and therefore surviving archives was the Communist Party Archives under the Central Committee of the Communist (Bolshevik) Party of Belarus, which was not part of the SAF of the BSSR. It was moved to Ufa and re-evacuated to Mogilev in the fall of 1944, its integrity allows us to fill up the documentary gaps formed in the State Archival Funds of the republic. With the beginning of the liberation of Belarus in the Autumn of 1943, the network of the republic’s archival institutions was restored, and the work was under way to identify and return to the republic the archival funds taken out by the invaders. The archives started collecting the documents and materials created by the partisan brigades and underground resistance organizations which were operating on the temporarily occupied territory of Belarus. Thanks to the dedicated work of the Belarusian archivists, it became possible to at least partially restore the archival funds of the republic, significantly damaged during the war.