Drawing on data from a three-wave longitudinal study, the present research examined predictors of young adults’ intentions to participate in politics and their actual political activities while referring to the broader assumptions of the theory of planned behavior. The analyses were based on a sample of university students from the federal state of Thuringia, Germany. The results showed that attitudes toward political behaviors and internal political efficacy beliefs explained changes in students’ intentions to participate in politics. However, the perceived meaning that political participation has for important others had no additional effect. Furthermore, students’ intentions to participate in politics and their internal political efficacy beliefs predicted changes in their actual behaviors. Together, the findings supported the theory of planned behaviors as a useful framework helping to predict young adults’ intentions and actual involvement in political activities.