Emotional dysregulation is a core component of borderline personality disorder (BPD). Theoretical models suggest that deficits in labeling physiological sensations of emotion contribute to affective instability in BPD. Interoceptive awareness refers to the ability to perceive changes in internal bodily states, and is linked to the subjective experience and control of emotions. The authors tested whether differences in interoceptive awareness accounted for emotional instability in BPD. Patients diagnosed with BPD (n = 24) were compared to healthy controls (n = 30) on two established measures of interoceptive awareness, a heartbeat perception task and a heartbeat monitoring task. Contrary to their hypothesis, the authors observed no significant differences in objective measures of interoceptive awareness. Their findings provide strong evidence against the notion that difficulties in emotional regulation in BPD are connected to differences in interoceptive awareness.