Self-harming behavior is a core symptom of borderline personality disorder. Self-report studies show a correlation between a lack of self-reported negative feelings toward self-cutting cues and the likelihood of future self-destructive behavior. Despite these findings, there has so far been insufficient investigation into the implicit emotional processes evoked by this stimulus type. Forty patients with borderline personality disorder and 35 healthy controls between 20 and 50 years of age were confronted with pictures of self-cutting cues and affective reference pictures. A startle reflex paradigm was used for measuring implicit emotional responses, and the Self-Assessment Manikin was used for subjective responses. In line with previous studies, the patients rated the self-cutting pictures significantly less negatively than healthy individuals. On the physiological level, a significant startle inhibition was observed, indicating an activation of the behavioral approach system. A more detailed analysis showed that this startle inhibition effect was specific to scary pictures, whereas no such effect was observed for bloody wounds and self-cutting instruments. For pleasant standard pictures, in contrast, no startle reflex inhibition and no increase in emotional arousal parameters were found. The data replicate the findings of previous studies, demonstrating a generally diminished emotional reactivity to pleasant stimuli in patients with borderline personality disorder. In addition, a physiological approach reaction to self-cutting pictures was found, especially for the scary pictures. These results might indicate a positive identification with the long-lasting consequences of self-cutting behavior in the patients. Implications for therapy are discussed.