This studies the effect of the 2018 US-China “Trade War” on firms’ stock market performance in both US and China. Based on the event-study approach, we find heterogeneous effects across listed companies, depending on their exposure to US-China trade. Specifically, we find that US companies in industries that are more dependent on exports to and imports from China had lower cumulative raw and abnormal returns, but higher default risks, around the day (March 22, 2018) when Trump’s administration announced the first wave of tariff protection against Chinese imports. We also find that the extent and pattern of companies’ participation in global value chains matter. US companies in sectors that are more exposed to Chinese imports and exports directly and indirectly through input-output linkages reacted more negatively to the “Trade War” announcement. Chinese companies that depend more on sales in the US and US companies that rely more on targeted Chinese products as inputs took a larger hit.