Harari, Shamay-Tsoory, Ravid, and Levkovitz (2010) demonstrated a "double dissociation" in empathy in borderline personality disorder (BPD), such that BPD patients had higher affective than cognitive empathy, whereas controls exhibited the opposite pattern. Two processes that may relate to this dissociation are emotion dysregulation (ER) and hypermentalization. However, these interrelated processes have not been studied concomitantly, and the dissociation of empathy types has not been examined in adolescents with BPD. This study examined the relations between ER, hypermentalization, and cognitive and affective empathy in 252 adolescent inpatients with and without BPD. Participants completed a computerized task of hypermentalization and measures of ER and empathy. Findings only partially replicated Harari et al.'s findings, with differential performance in cognitive and affective empathy demonstrated across groups. Multivariate analyses revealed that in both groups, ER related to increased affective empathy. Hypermentalizing related to decreased cognitive empathy in BPD patients, whereas hypermentalizing did not relate to either empathy type in non-BPD patients.