Compulsory voting does not only increase voting turnout; it is also expected to have positive spill-over effects. Supposedly, citizens who are obliged to cast a vote will be more engaged in politics than citizens who are allowed to avoid politics. This article reviews the main arguments for this expectation. A rival expectation is formulated based on the idea that enforcements, duties and sanctions are likely to decrease the willingness of citizens to participate politically. A cross-national multi-level empirical test – covering turnout and political participation in twenty established democracies – shows that compulsory voting indeed increases voting turnout. Yet neither positive nor negative spill-over effects for other modes of political participation can be detected. Apparently, the consequences of compulsory voting are restricted to turnout.