While increasing trade and foreign direct investment, international trade agreements create winners and losers. Our paper examines the distributional consequences of preferential trade agreements (PTAs) at the firm level. We contend that PTAs expand trade among the largest and most productive multinationals by lowering preferential tariffs. We examine data covering the near universe of US foreign direct investment and disaggregated tariff data from PTAs signed by the United States. Our results indicate that US preferential tariffs increase sales to the United States from the most competitive subsidiaries of multinational corporations operating in partner countries. We also find increases in market concentration in partner countries following preferential liberalization with the United States. By demonstrating that the gains from preferential liberalization are unevenly distributed across firms, we shed new light on the firm-level, economic sources of political mobilization over international trade and investment policies.