This study investigates the impacts of the COVID-19 lockdown on municipal solid waste (MSW). Based on a unique data set of daily discarding records of 252 communities in Beijing, China, we conduct a difference-in-differences estimation and find that the total daily MSW decreased by 134.16 kg in a community, which is equivalent to at least 0.22 kg per household per day, and the average weight of MSW per package decreased by 56.8 per cent after the COVID-19 lockdown. We consider a series of potential mechanisms, such as MSW hoarding, shifts in discarding time, and fear of going out, and find the most support for consumption pattern shifts with reduced consumption. We then discuss the effect of the lockdown on the reduction of MSW generation because of the strict restriction of consumption. We also conduct various heterogeneity analyses. Our results present clear implications for municipal waste management by highlighting the effect of the lockdown on the generation of MSW and the underlying consumption mechanism.