The diagnosis of borderline personality disorder (BPD) in children is surrounded by controversy. Some authors emphasize the risks of giving early diagnoses, while others consider it essential for guiding treatment. An intermediate position involves identifying clinical indicators of the possibility of BPD developing in adulthood. These include the use of immature defense mechanisms. Children who have experienced traumatic events in their relationships with their parents, like those taken in by child protective services, are at an increased risk of developing BPD in adulthood. The present study explores the links between traits of borderline personality disorder and defense mechanisms among school-age children who have experienced traumatic events. The results show that certain borderline personality traits are linked to immature defense mechanisms, and inversely associated with mature defense mechanisms.