Research has shown that patients with a social anxiety disorder (SAD) show social performance deficits. These deficits are a maintaining factor in SAD, as mending social behavior improves interpersonal judgments and reduces social anxiety. Thus finding ways to enhance social behavior is evidently of importance in the treatment of SAD. This double-blind, placebo-controlled study investigated the effect of an intranasal administration of the hormone oxytocin (24 IU) on social behavior and anxious appearance in SAD patients (N = 40) and healthy controls (N = 39). Forty minutes after oxytocin administration participants were submitted to two live social situations (i.e., a waiting room situation and a getting acquainted task). The participants ('self-rated') and observers ('observer-rated') scored participants' social behavior and anxious appearance. Participants also rated their positive and negative affect. Confirming the social performance deficits in SAD, observers regarded SAD patients as more anxious and less socially skilled than healthy controls. Results indicated oxytocin-induced improvement of observer-rated social behavior in SAD patients compared to placebo but only in the getting acquainted task. This effect was not perceived as such by patients themselves and did not improve their affect ratings. In conclusion, this study found support for the idea that oxytocin helps SAD patients to perform better in social interactions, although this improvement seemed context-dependent (i.e., only present in the getting-acquainted task) and 'not perceived by the patient.