Social media use occupies a prominent space in social sciences scholarship and beyond. However, the distinction between active and passive use of social media, although important in explaining a variety of users’ behaviors, has been overlooked in terms of its potential to predict key outcomes like beliefs in conspiracy theories. In three studies (N = 1388, in total), we provide evidence on (a) the role of passive social media use in believing in conspiracy theories via personal relative deprivation; (b) the interaction effect between social media use and personal relative deprivation on beliefs in conspiracy theories. Results showed that passive social media use is linked to, and has a positive effect on, beliefs in conspiracy theories and this relationship is explained via increased personal relative deprivation. Additionally, this main effect was qualified by an interaction with increased personal relative deprivation. Results are discussed in light of their social and media psychological contribution and implications in the digital era, an era of fighting, out of many, against misinformation.