In the mid-19th century, the Russian government started pushing forward the implementation of a policy to move its population eastward. This was done to strengthen the country’s position in the East and required coordination with China to establish state borders. The legal formalization of the boundaries resulted in the development of new mechanisms of border diplomacy for further interaction between both countries. However, there has been relatively little study of the approaches and tools used in Russian-Chinese diplomacy during this time. This article summarizes the history of establishing border commissariats on the Russian-Chinese border in the 2nd half of the 19th – early 20th century. The study is carried out using the narrative, structural, and functional method, the method of variance, and normative comparison. As a result, it finds out that in the 2nd half of the 19th century, diplomatic functions were shared between the Governor-General, border commissars, and diplomatic officials reporting to the Governor-General. The border commissar was a civil position of the Ministry of Foreign Affairs and was represented by a civilian with the rank of state adviser. The Commissioner’s powers were subordinated to and supervised by the Far East region's Governor-General (military position), who overlooked diplomatic relations. Four border commissariats were set up in the Transbaikal, Amour, South Ussuri and Uryankhay regions. The author concludes that there was no unified system of border commissariats. Although the commissars shared professional duties, they acted independently and dealt with foreign policy issues specific to their region. Overall, the commissars' activities helped maintain socio-political stability in the Eastern border regions of the Russian Empire.