Background : Transdiagnostic emotional vulnerabilities are suspected to underlie psychopathologic comorbidity but have received little attention in adolescent emotional pathology literature. We examined distress tolerance, anxiety sensitivity, and anhedonia as concomitant transdiagnostic mechanisms that account for (i.e., statistically mediate) the covariance between adolescent obsessive‐compulsive disorder (OCD) and major depressive disorder (MDD) symptoms. Method Data on MDD, OCD, and the three aforementioned transdiagnostic vulnerabilities were collected from a community‐based sample of 3,094 ninth graders in a large metropolitan area and analyzed using mixed effects modeling to evaluate mediation effects. Results Individually and when controlling for each other, all three transdiagnostic vulnerabilities mediated the relation between OCD and MDD symptoms both before and after adjusting for demographics. Conclusions Distress tolerance, anxiety sensitivity, and anhedonia may be unique mechanisms accounting for comorbidity between OCD and MDD symptoms in youth. Longitudinal evaluation of these candidate transdiagnostic emotional vulnerabilities in adolescent OCD‐MDD comorbidity is warranted.