Studies have found large differences in masks use during the pandemic. We found evidence that cultural tightness explains mask use differences and this association was more robust in tight situations like subways. In Study 1, we observed 23,551 people's actual mask use in public places around China. People wore masks more in tight situations; however, differences did not extend to outdoor streets and public parks, where norms are looser. We replicated this finding using a data from 15,985 people across China. Finally, in a preregistered study we observed mask use with the removal of COVID-19 restrictions, people still wore masks more in tight situations like subways than in loose situations of parks. These findings suggest that norm tightness has a lasting association with people's health-protective behaviors, especially in tight situations. It provides insight into how different cultures might respond with future pandemics and in what situations people adopt health-protective behaviors.