A large and coherent body of evidence reveals that individuals higher in dispositional mindfulness fare better than their less mindful counterparts on a range of psychosocial outcomes. However, few studies have examined the effects of dispositional mindfulness on adolescent mental health, and potential mechanisms underlying its salutary effects. The aim of the present research was to examine whether low dispositional mindfulness was associated with heightened depression, anxiety, stress, internalizing symptoms, and externalizing symptoms in a sample of adolescents (N = 113, Mage = 14.9 years), and whether two emotion regulation strategies, namely cognitive reappraisal and expressive suppression, mediated any association. Results revealed that low mindfulness was associated with poor functioning across all indices of psychopathology. Further, expressive suppression, a maladaptive emotion regulation strategy, mediated associations between low mindfulness and depression, anxiety, and stress. In brief, dispositional mindfulness appears to be a protective individual difference characteristic during adolescence, and capacity for emotion regulation may be implicated in its effects on specific symptoms of psychopathology.