Based on the multinational panel data of countries along the Belt and Road Initiatives from 1990 to 2016, applying the bias-corrected LSDV estimator, this paper estimates the impact of foreign trade and financial development on carbon emissions. The study finds that foreign trade and financial development have complementary roles in reducing carbon emissions. Foreign trade is harmful to the environment when financial development is low but turns beneficial when financial development is high. Also financial development will be environmentally improving only in countries with the high foreign trade. In addition, from the results of empirical tests based on income and regional samples, the interaction effect of trade finance on the environment only supports middle-income countries. In high-income countries, due to development differences, the statistical results are not significant. In non-Asian regions, the complementarity of foreign trade and financial development has a greater impact on carbon emissions than in Asia.