The goal of the current study was to investigate subjective and neurohormonal reactivity to acute psychosocial stress in borderline personality disorder (BPD) as a function of dissociative symptoms. Five BPD subjects with high dissociation, 8 BPD subjects with low dissociation, and 11 healthy control subjects were compared in basal urinary cortisol and norepinephrine, as well as in plasma cortisol and norepinephrine reactivity to the Trier Social Stress Test (TSST). Subjective stress rating and emotional response to the TSST were also measured. The three groups differed significantly in cortisol stress reactivity, with the high-dissociation BPD group demonstrating the most robust response. The three groups did not significantly differ in norepinephrine stress reactivity. In the combined BPD sample, dissociation severity tended to be inversely correlated with basal urinary norepinephrine, was positively correlated with norepinephrine stress reactivity. Childhood trauma was inversely correlated with basal urinary cortisol. In conclusion, despite its small sample size this pilot study suggests that dissociative symptomatology may be a marker of heightened biological vulnerability to stress in BPD, and merits further study.