Objective <p>Based on the Self-Determination Theory, this study examined the influences on adolescents’ subjective well-being and revealed the chain mediating role of physical activity and socio-emotional competence between exercise motivation and subjective well-being.</p> Methods <p>Motives for Physical Activity Measure (MPAM-R), Subjective Well-Being Scale for Chinese Citizen (SWBS-CC20), Physical Activity Rating Scale (PARS-3), and The Delaware Social-Emotional Competency Scale (DSECS-S) were used to conduct questionnaire surveys on 1,530 junior high school students in Handan, Hebei Province. The data were statistically analyzed by using the SPSS 23.0 and AMOS 23.0 software.</p> Results <p>(1) There is a positive correlation between exercise motivation and subjective well-being, and the direct prediction of subjective well-being is significant; (2) Exercise motivation can indirectly influence adolescents’ subjective well-being through the partial mediation of physical activities and social-emotional competency; (3) Exercise motivation may also indirectly affects adolescents’ subjective well-being through the chain mediation of “physical activities and social-emotional competency”.</p> Conclusion <p>A higher EM may enhance adolescents’ level of PA and SEC, which further contributes to their SWB, which plays an important role in enhancing adolescents’ mental health and maintaining a healthy lifestyle.</p>