This article aims to analyze the foreign trade of border municipalities in the extreme south of Rio Grande do Sul, in the context of regional integration debates. The focus is on the twenty-one Brazilian municipalities located in the Mirim-São Gonçalo Hydrographic Basin - whose waters are transboundary - situated on the limits of the Border Strip determined by Law nº 6.634, of May 2, 1979. Considering that the literature on regional integration suggests that the effects of such arrangements are the strengthening of links between the actors involved, we seek to analyze the profile of foreign trade in these municipalities to prove or refute the initial hypothesis that the municipalities of the Mirim-São Gonçalo Hydrographic Basin are integrated in terms of trade with the neighboring country, Uruguay. This is a qualitative study, based on primary and secondary sources and has an analytical-descriptive purpose. From the data obtained, it can be concluded that although in terms of values, foreign trade with Uruguay is not so representative, a portion of the municipalities that carry out foreign trade operations do business with the country. It is suggested that future studies deepen the discussions on production chains in the region.