Social network sites such as Facebook and Twitter have become a key part of online users? news diets. On social network sites, even individuals who are not motivated to seek out news are believed to be exposed to news posts due to the sharing activities of friends or inadvertently witnessing discussions about current events. Research on this incidental news exposure (INE) has largely focused on its potential for positive effects on information gain or political participation, while simultaneously turning a blind eye to the inequalities in news exposure and engagement. This article aims to address this issue by proposing and explicating the existence of a ?Matthew Effect? in social media news use. It is argued that INE research needs to consider the unequal chances to both be exposed to news on social network sites and to actually engage (i.e. read and interact) with ?accidentally? encountered news content.