INTRODUCTION: Adolescents higher in the trait of dispositional mindfulness report fewer socioemotional problems. Focusing on the domain of peer stressors, we tested a model of adolescents' mindfulness as a resource that undergirds more constructive stress coping responses, in turn resulting in fewer socioemotional problems. METHOD: The participants were 361 Australian secondary school students (40% boys; ages 11 to 18; M = 14.9 years; SD = 1.4). Each completed a questionnaire to report four facets of dispositional mindfulness; engagement and disengagement coping and involuntary stress responses to recent peer interpersonal stressful events; and socioemotional problems of loneliness, social anxiety, and depression. RESULTS: Adolescents who reported more dispositional mindfulness, including facets of awareness, describing, non-judgement and non-reactivity, were lower in involuntary peer stress responses, disengagement coping, loneliness, social anxiety, and depression; associations of mindfulness facets with engagement coping were mixed. Mediational path models showed that almost all the significant negative associations of dispositional mindfulness with loneliness, social anxiety and depression were fully indirect via peer stress coping responses. Further, an alternative model, which tested whether loneliness, social anxiety and depression were the instigators of stress coping responses via mindfulness, had an adequate but poorer fit. CONCLUSION: As hypothesized, the benefit of adolescents' dispositional mindfulness for reducing loneliness, social anxiety and depression seems to be indirect, with positive peer stress coping responses key mediators in these indirect pathways. It is less likely that the alternative occurs, whereby adolescents' socioemotional problems are the foundation for mindfulness and peer stress coping responses.