We study the financial impact of the 2018-2019 U.S.-China trade war on firms engaged in global supply chains. Around the dates when higher tariffs were announced, U.S. firms depending more on exports to and imports from China experienced larger declines in market values. Guided by a model that identifies various direct and indirect trade channels through which tariffs affect firms' profits, we examine the transmission of tariff shocks through firms' suppliers and customers. We confirm our results by exploiting the within-firm variation in product exposure based on two tariff lists and a positive trade negotiation as a reverse experiment.