Scholars agree that institutional and non-institutional (i.e., protest) politics are increasingly interrelated. One expression of this phenomenon is party protest – when leaders, activists, or sympathizers of political parties participate in protest events and identify themselves as such. Yet we know little about how often parties partake in protests, which ones do so, and under which conditions. Using data on more than 2,300 protest events in Chile between 2000 and 2012, I show that party protest takes place in only 6% of all protest events, and that it is essentially monopolized by leftist parties. Additionally, by combining several strands of the literature on political parties and collective action, I derive hypotheses about the impact of the features of protest events and the broader national context on the chances of party protest. Multivariate regression models show that party protest is more likely in events which take place in highly visible locations and are coordinated by other civil society organizations. Additionally, party protest occurs when the center-left coalition is in power and when collective protest at the national-level is less intense and less transgressive.