From 2013 to 2015, China gradually established nationwide air quality monitoring stations and began to release real-time air pollution information to the public. We exploit step-by-step environmental regulations across cities to identify the effects of information disclosure on air pollution. We find that information disclosure significantly decreases the concentrations of PM2.5 and PM10. Through mechanism analysis, we find that information disclosure raises the level of government awareness, increases the amount of investments in air pollution prevention and control, stimulates green innovation, and forces heavily polluting enterprises to shut down. Additionally, we find evidence that the effectiveness of information disclosure varies across cities.