This experiment investigates the emotional consequences of viewing strangers’ positive posts on Instagram. From a social comparison perspective, strangers’ positive posts on social media are expected to negatively affect viewers’ emotions. From an emotional contagion perspective, strangers’ positive posts should positively affect viewers’ emotions. The current lab experiment examines both the social comparison and the emotional contagion perspective while taking individual differences into account. Participants viewed positive, neutral, or no posts of confederates. In support of the social comparison perspective, individuals who tend to compare themselves to others reported lower positive affect if they had viewed positive posts than if they had viewed neutral or no posts. In support of the emotional contagion perspective, individuals who tend not to engage in social comparison reported higher positive affect after viewing positive posts than after viewing neutral or no posts. These findings indicate that individual differences in processing tendencies lead people to respond to social information on social media in opposite ways.