In the publication foreign published and unpublished sources on history of peace negotiations in Brest-Litovsk. The authors note that for the last century in different countries of Europe and in the USA a large number of collections of documents and memoirs on this problem have been published. Nevertheless, documents of archives are still almost unused. Important documents are stored in Austrian State Archive, Central state archive of Bulgaria, The state military-historical archive of Bulgaria, Political Archive Of The Federal Foreign Office of Germany, The Archive of The Ministry of Foreign Affairs of Turkey, The branch state archive of the Ministry of foreign Affairs of Ukraine, The Central state archive of Supreme bodies of power and administration of Ukraine. The introduction of previously unused archival documents into scientific turn will allow to investigate a problem at qualitatively new level.