ENThis article is dedicated to the issue of Polish and Russian language contacts in the 16th and 17th centuries. The analysed Old Belarusian historical assets document the presence of foreign vocabulary assimilated via the Polish language. Research shows that the Polish Language of that period formed a medium used to transfer words of German, Latin, Czech or Italian origin to the Belorusian land. The functioning of such borrowings has been tracked on the basis of two popular literary genres on the territory of the Grand Duchy of Lithuania – chronicles (Kronika Supraska and Kronika Bychowca), representing original Belorusian literature, and chivalric romance (Białoruski Tristan), which was an example of translated literature. Loanwords supplemented native lexical resources with lacking units to name such areas as state, church and military institutions, living needs, war craft and the life of knights. Key words: Grand Duchy of Lithuania, language contacts, Old Belarusian literature, Polish Language, lexical borrowings.