ABSTRACT Mass media have long been known to be deeply linked to ethnocentrism and its consequences. Attitudes towards ethnic outgroups are shaped by news agendas, framing, and tone at least as much or more than by the realities of immigration. By contrast, comparatively little is known about social media and interethnic contact. Unlike mass news, the interactive features of social media use can combine information with a direct interethnic contact. This creates an online public sphere which has the potential of being ethnically more diverse than the offline public sphere. By reviewing and connecting the literature on intergroup contact and online political communication, the given study attempts to connect the optimal intergroup contact theory by Gordon Allport to the realities and affordances of social media. The empirical analysis relies on a three-country survey with 4532 respondents in France, the United Kingdom, and the United States. Mindful of the endogeneity problem in our cross-cutting data, we perform propensity score matching and find that spending more time on X (formerly Twitter) is correlated with lower intergroup ethnocentrism under randomized conditions. No such effect was found for Facebook. We also find that people who discuss politics with those that have different ethnicity or race via social media (or offline) are less ethnocentric.