Introduction: Current literature recognizes that various socialization agents often shape political behavior. This study employs frameworks of political socialization and political agency to explore how extracurricular activities and political intentions established at age 16 influence aspects of political participation and civic engagement at age 20. Methods: A 4-year longitudinal study was conducted using a community-based sample of 933 adolescents from a medium-sized Swedish city with a population of approximately 135,000. Data were collected in 2010 and 2014, allowing for an analysis of the impact of extracurricular activities and political intentions developed during adolescence on later political and civic behaviors. The analytical sample comprised 933 individuals (50.8% females; mean age = 16.62, SD = 0.71). Results: The analysis revealed that participation in extracurricular activities at age 16 is a significant predictor of offline political participation at age 20. However, no significant associations were found between these activities and other forms of participation, such as illegal behaviors or broader civic engagement. Political intentions at age 16 also significantly predicted offline political participation at age 20. Conclusions: The findings highlight the pivotal roles of both socialization agents and individual factors related to youth political agency in shaping political trajectories during adolescence. Understanding the effects of extracurricular activities and political intentions on political participation and civic engagement can aid policymakers and educators in developing strategies to foster active citizenship among young people.