The bourgeoning literature on the protestors of the Arab Uprisings proposed several arguments about participation in protests in reference to grievances and opportunities. However, these arguments did not directly test both grievances and opportunities in a comparative setting. Using survey evidence, this article explores the role of grievances and opportunities on participation in protests in Egypt and Tunisia. It argues that grievances for Tunisians and opportunities for Egyptians played the main role for the decision to participate. Particularly, the Egyptians who followed the news and the developments in Tunisia more closely perceived such an opportunity to protest against their regime.