This study seeks to broaden the understanding of socioeconomic health disparities among Korean adolescents. Specifically, we examine the pathways from objective SES and subjective SES to physical health through a psychosocial perspective. To this end, stress and self-efficacy, which have been identified as critical psychosocial factors associated with SES, and physical activity, one of the most representative health behaviors during this period, are included as mediating variables in the research model. We utilize data from the 3rd year survey of the Seoul Education and Health Welfare Panel (2016), which consists of responses from 680 adolescents and parents. Structural equation modeling is used to analyze the responses. The results show that sSES is directly associated with the physical health of adolescents. Meanwhile, oSES is indirectly associated with physical health and has two distinct psychosocial pathways to physical health according to whether or not the effect is mediated by sSES. Finally, we discuss the implications of the study findings.