Pain is rarely suffered alone. In contemporary online contexts, publicly shared pain can command the collective attention of hundreds, even millions of people. We sought to explore the possibility that collectively attending to others' pain promotes affiliation among those with whom it is attended online and identify the mechanisms that mediate these effects. Across two experimental studies, utilizing independent group designs, physically dispersed undergraduate students attended to real-world videos depicting either physical, social, or no-pain online. In Study 1 (N = 74, 66.22% female, Mage = 25.31 years, SDage = 6.81 years), we found evidence for the phenomenon of pain collectively attended to online, with online videos depicting physical and social pain eliciting stronger perceptions of collective attention than the non-painful online video. In Study 2 (Time 1: N = 185, 75.14% female, Mage = 22.62 years, SDage = 7.44 years; Time 2: N = 91, 72.53% female, Mage = 23.32, SDage = 8.19), we subsequently found collectively attending to others' physical and social pain online indirectly promoted cohesion, interpersonal closeness, and desire to affiliate among participants through perceived emotional synchrony. This pattern of indirect effects was found immediately after collective attention to painful online content (Time 1) and at 1-week follow-up (Time 2). Although preliminary, our findings increase practical understanding of how shared pain can be harnessed to bond physically dispersed individuals together online, the implications of which we discuss in the context of the COVID-19 pandemic.