Patients with borderline personality disorder (BPD) display disturbances in self and other understanding, which is also evident when they narrate events from their own and significant others' lives. In a recent study, we found that patients described both their own and their parents' life stories as more negative and with fewer themes of agency and communion fulfillment. Hence, we examined whether 12 months of psychotherapy would change how patients described their own and their parents' life stories. At baseline, 30 BPD patients and 30 matched control participants described and answered questions about their personal and their parents' life stories. At follow-up, 23 patients and 23 control participants repeated the same procedure after patients had completed 12 months of psychotherapy. At both baseline and follow-up, the life stories were coded for complexity and themes of agency, communion, communion fulfillment, and self-other confusion. BPD patients' personal life stories increased significantly in agency from baseline to follow-up compared with the control group, whereas other aspects of personal and parents' life stories did not change significantly after therapy. Development of agency through the reconstruction of personal life stories may be a crucial mechanism in psychotherapy with BPD patients.