Abstract: Feelings of dissatisfaction with the political status quo are believed to mobilize citizens into non-institutional political action, such as protest. Still, little is known about whether and how political participation through social media provide an alternative voicing route for discontented citizens. Guided by grievance theory, this article assesses how both electoral exit behaviour (e.g., abstaining) and attitudes of political discontent (political and media trust, political hopelessness and populism) are associated with three modes of non-electoral political participation: institutional, protest and social media participation. An online survey was administered to 720 young adults between 18 and 30 years old in Belgium. A hierarchical regression analysis showed no association between electoral exit and non-institutional participation. Furthermore, attitudes of discontent were found to not uniformly push young citizens away from institutional politics. Our results show that social media provide an important, additional political outlet for young citizens and lend support to the notion of political participation as complementary acts, rather than exclusive ones.