The literature has extensively explored the relationship between trade and envi-ronment, with most studies focusing on how trade affects the environment. However, our research takes a different approach by examining how air pollution affects firms’ exports. We use Chinese export and pollution data from 2000 to 2007 at the firm and county levels. By using fine particulate matter (PM2.5) concentrations as a proxy for air pollution and employing thermal inversion as an instrumental variable, we ffnd that a 1% increase in PM2.5 leads to a 0.89% reduction in firms’ exports. We also observe this negative effect of air pollution on entry and exit (i.e., extensive margins). Our mechanism analysis identiffes two channels through which air pollution affects exports. First, air pollution decreases exports by reducing firm productivity. Second, air pollution induces stringent environmental regulations, which reduces exports as firms need to increase abatement costs or reduce production to meet the environment standards.