**Abstract.** Marketing on social media has become ubiquitous. Consequently, social media platforms are increasing the level of advertising content that users may later encounter when navigating online shopping websites. It is unclear how this amplification of exposure to marketing messages through social media affects consumers’ attitudes to products online. Further, the roles of social media participation and proneness to experience Fear of Missing Out (FOMO) on product attitude remain largely unexplored. In this research (N = 1,002), we employed an online survey of U.S. Instagram users. These data were submitted to three-way moderation regression analyses with attitude toward the product as the dependent variable. Consumers who are more active on social media and had high (versus low) FOMO expressed more favorable attitudes toward online products after being exposed to Instagram content (versus not exposed). The theoretical and practical implications for cognitive processing research and advertising strategy and study limitations are discussed.