Individuals with borderline personality disorder (BPD) have difficulties regulating emotions, which may be a consequence of using less effective emotion regulation (ER) strategies to lessen the intensity of their negative emotions. It is not yet known whether people with BPD utilize particular ER strategies to modulate specific mood states and if these strategies are different from those used by individuals with depressive and anxiety disorders. In the present study, 90 participants (30 BPD, 30 anxiety and/or depressive disorders, and 30 healthy controls) underwent a mood induction procedure and specified which ER strategies they used and their perceived difficulty regulating mood following induction. Compared with healthy controls, BPD endorsed higher negative mood prior to, immediately following, and 4 min after neutral and negative mood inductions; more maladaptive ER strategies (e.g., rumination); and more perceived difficulty regulating negative mood. Compared with anxiety and/or depressive disorders, BPD endorsed similar ER strategies and subjective difficulty during mood inductions, endorsed higher negative mood following a neutral video and 1 negative video, and recorded higher RSA reactivity during and following 2 negative videos. Results suggest that individuals with BPD use a higher number of maladaptive ER strategies compared with healthy controls, which may lead to less effective modulation of negative mood and higher reports of difficulty regulating emotions. In addition, physiological measurements indicated that individuals with BPD may have higher RSA reactivity in response to negative mood induction compared with other mental disorders, which may reflect inefficient or disorganized attempts to regulate emotional arousal.