The present study investigated the mediating processes of emotional awareness, positive emotions, and negative emotions between music engagement and well-being among Chinese adolescents. Through a process-oriented approach, the association between music engagement activities, including music listening, music instrument playing, and music training, and adolescents' functioning were examined. A total of 1,318 Chinese adolescents at 12-15 years of age were recruited from secondary schools in Hong Kong. Findings based on structural equation modeling provided differential support for the association between music engagement and adolescents' well-being. As cognitive and affective processes, both emotional awareness and emotions mediated between music training and well-being. Positive and negative emotions also mediated between music listening and adolescents' well-being. Surprisingly, music instrument playing was not associated with emotional awareness, positive or negative emotions, or well-being. These findings supported previous frameworks and call attention to the emerging mechanisms underlying music engagement and well-being in adolescence.