This study examined the effects of media use on preventive behavior during the COVID-19 pandemic using a two-wave panel survey in Japan (2020 and 2021). Results showed that the effect of social networking service (SNS) browsing on preventing going out was only observed in the early pandemic stage and not a year later. Changes in behavior from self-restraint to going out were influenced more by cognitive factors than media use. The study highlights the importance of time-series analyses in understanding the dynamic relationship between media and preventive behaviors during pandemics.