Potentially traumatizing experiences by a primary caregiver during childhood (TPC) may lead to affect dysregulation, which is a hallmark of borderline personality disorder (BPD) in adulthood. Path analyses with bootstrap confidence intervals were used to explore the relationships of TPC and under- and overregulation of affect to BPD symptoms. Almost 63% of a sample of 472 patients diagnosed with either BPD alone, comorbid BPD + somatoform disorder, or other mental disorder, reported childhood TPC.