In this study, we propose that social media reduce users' moral sensitivity through the mediation of the perceived moral intensity of hostile comments, which leads to behavioral consequences for online shaming. Three separate studies were conducted to explore this statement. Study 1 (N = 160) compared moral sensitivity between participants in simulated social media situations and a control group. Study 2 (N = 412) tested the mediating role of perceived moral intensity through self‐rated questionnaires. Study 3 (N = 295) examined the behavioral consequences of reduced moral sensitivity on online shaming by manipulating social media and perceived moral intensity. Across these three studies with their different methodologies, we found consistent support for our prediction that social media reduce users' moral sensitivity. Also, our findings shed light on perceived moral intensity as a mediator. As expected, less perceived moral intensity and less moral sensitivity (as serial mediators) induced by social media led to a higher tendency to participate in online shaming. In addition, our research suggests that the harmful effects of social media could be restricted by improving users' perceived moral intensity in the form of reminders. These findings provide novel insights into the underlying mechanism of cyberviolence on social media and also contribute to the literature on the antecedents and consequences of moral sensitivity.