Patients with Borderline Personality Disorder (BPD) have been described as emotionally hyperresponsive, especially to anger and fear in social contexts. The aim was to investigate whether BPD patients are more sensitive but less accurate in terms of basic emotion recognition, and show a bias towards perceiving anger and fear when evaluating ambiguous facial expressions. Twenty-five women with BPD were compared with healthy controls on two different facial emotion recognition tasks. The first task allowed the assessment of the subjective detection threshold as well as the number of evaluation errors on six basic emotions. The second task assessed a response bias to blends of basic emotions. BPD patients showed no general deficit on the affect recognition task, but did show enhanced learning over the course of the experiment. For ambiguous emotional stimuli, we found a bias towards the perception of anger in the BPD patients but not towards fear. BPD patients are accurate in perceiving facial emotions, and are probably more sensitive to familiar facial expressions. They show a bias towards perceiving anger, when socio-affective cues are ambiguous. Interpersonal training should focus on the differentiation of ambiguous emotion in order to reduce a biased appraisal of others.