Objectives: This study identified the direct effects of parent–adolescent communication on middle school students’ subjective well-being and the mediating effects of positive psychological capital on this process. Methods: Participants in this study consisted of 234 middle school students (114 males, 118 females) living in Gwang-ju city, Korea. Participants were 234 middle school students in Gwang-ju city, who completed a self-report questionnaire, including measures of parent–adolescent communication, positive psychological capital, and subjective well-being. Data were analyzed using PASW ver. 18.0 and AMOS ver. 18.0 to conduct descriptive statistics, correlation analysis, and a structural equation model (SEM). Results: First, open parent–adolescent communication had a positive influence on subjective well-being in middle school students, but problematic parent–adolescent communication had a negative influence on subjective well–being in middle school students. Second, positive psychological capital had a positive influence on subjective well-being in middle school students. Third, positive psychological capital acted as a partial mediator for parent–adolescent communication, affecting subjective well-being in middle school students. Conclusion: This study highlights the fact that parent–adolescent communication has an effects on middle school students’ subjective well-being via positive psychological capital. This study contributes to the literature by providing fundamental insights into subjective well-being in middle school students.