The article investigates trade flows between the Shanghai Cooperation Organization (SCO) member-states and Belarus before the upcoming Belarus’ joining the organization. The export flows of the countries are modeled using a power function based on the time data. The results of the qualitative and quantitative analysis of foreign trade between the organization and the Republic of Belarus are presented, as well as the quantitative forecast of the prospects open to Belarus in connection with its joining the organization based on three original scenarios using econometric models. The results of the study show that Belarus has certain promising sectors of foreign economic activity, which can contribute to an increase in income from trade. It was found that the integration of the country will have a positive effect on increasing the volume of trade turnover with the participating countries, while in order to maintain sustainable economic growth of the country, domestic development of production should remain a priority, as evidenced by the obtained parameter estimates for the factors. An assessment of potential economic effects can be used to make a decision on whether a country should join an international organization. In particular, based on the assessments in our study in trade with Russia the expected increase in Belarus exports upon joining the Shanghai Cooperation Organization will constitute an increase of nearly 5%, exports to Kazakhstan are expected to increase by almost 75%, and to India and China by almost 90%. In the context of reshaping of international associations and organizations, the problems and issues raised in the study become even more relevant.