Adolescents’ political socialization is crucial for their future political participation. Little research has examined this relationship and the importance of citizenship self-efficacy in an Asian context. This study focused on the effectiveness of Korean adolescents’ political socialization and self-efficacy on their expected electoral participation. Data from Korean 8th graders participating in the 2016 International Civic and Citizenship Education Study were examined (N = 2601; Mage = 14.02; 46% female). Political socialization included open classroom discussion, active learning strategies, and formal citizenship education. The result showed that citizenship self-efficacy is the most important predictor for Korean adolescents’ future engagement, but open classroom discussion is not significant. It indicates that citizenship education needs to consider countries’ social and cultural contexts.