Background: Families and significant others of people with borderline personality disorder (BPD) show increased levels of psychological distress. Family Connections®, a 12-week group intervention based on the principles of Dialectical Behavior Therapy, was designed to provide families with both information about the disorder and emotion regulation skills. It has been progressively implemented in French-speaking European countries. Methods: We conducted an observational, multicenter study in France and Switzerland. In total, 149 participants of the Family Connections program were included among five centers. Burden, depression, coping, and emotion regulation were assessed before and after the intervention. Results: One-way repeated measures MANOVA showed that the burden, depressive symptoms, emotion regulation and coping all changed significantly after the intervention (p < 0.001, partial η2 = 0.297). T-tests showed that the burden significantly decreased after the intervention (p < 0.0001, d = -0.48), as did depressive symptoms (p < 0.0001, d = -0.36) and difficulties in emotion regulation (p < 0.0001, d =-0.32) whereas coping improved (p < 0.0001, d = 0.53). Two-way mixed ANOVA showed that burden reduction was stronger among female than male participants (p = 0.048, η2 = 0.027). Before the intervention, the burden was higher for female than male participants (p < 0.001). An initial linear regression showed the burden reduction to be associated with a decrease in the resignation of the participants (β = 0.19, p = 0.047). A second linear regression showed the burden reduction to be associated with the intensity of the relatives' symptoms at baseline (β = 0.22, p = 0.008) and improvement of emotional clarity of the participants (β = 0.25, p = 0.006). Conclusion: This Dialectical Behavior Therapy-Based psychoeducational intervention is an appropriate way to support French-speaking European families of people with BPD.