This article analyzes the relationship between democratic discontent and protest participation. For this purpose, the article introduces a measure of democratic discontent that is better suited to test the arguments put forward by relative deprivation theory and that, at the same time, distinguishes between discontent related to the liberal and the social dimensions of democracy. Moreover, drawing on mobilization theories this article analyzes if the presence/absence of actors capable of mobilizing specific forms of democratic discontent in the protest arena moderates the relationship between democratic discontent and protest participation. The empirical results, based on data from the sixth round of the European Social Survey, indicate that democratic discontent is positively related to the likelihood of demonstrating. However, the strength of this relationship depends, first, on the specific dimension of democracy individuals are not satisfied with, and, second, on the presence/absence of actors, like political parties and trade unions, that can mobilize specific forms of democratic discontent in the protest arena.