OBJECTIVE: This study explored the role of emotion regulation (ER) as a moderator in the stressor-adjustment outcome relationship while identifying the relevant stressors. METHODS: In 214 adolescents (10-18 years; 51.4% boys), stressors (parent and peer relations, negative events), psychological outcomes (adolescent perceived stress, psychopathology symptoms, negative affect), and biological measures related to the stress response (hair cortisol [HC], heart rate variability [HRV]) as well as ER strategies-maladaptive (MalER), adaptive (AdER), and their ratio (Mal/AdER)-were measured and analyzed via linear regression, adjusted for age, sex, and socioeconomic status. RESULTS: Parental rejection and bullying were the stressors with the strongest association with psychological outcomes (beta range = |0.217-0.352|, p < .05). In addition, parental rejection was associated with HC (beta = 0.242, p = .035), whereas none of the stressors were associated with HRV. MalER was linked to all, and AdER to most psychological outcomes (beta range = |0.21-0.49|, p < .05). MalER, but not AdER, was associated with HC (beta = 0.25, p = .009), whereas none of the ER strategy types were associated with HRV. Moreover, several associations between stressors and psychological outcomes were moderated by MalER and Mal/AdER, whereas AdER\'s role as a moderator was not confirmed. CONCLUSIONS: The study confirmed that adolescents\' stressors are associated with both psychological and physiological outcomes and moderated by MalER or Mal/AdER. The lack of moderation by AdER directs toward the maladaptive shift theory. Investigations through a longitudinal, rather than a cross-sectional design, could further elucidate the current observations. Moreover, training in how to use ER effectively has a potential of increasing adolescents\' stress resilience.