The neuropeptide oxytocin is involved in the development and maintenance of attachment behaviours in humans and other species. Little is known, however, about how it affects judgements of unfamiliar others. In a double-blind placebo-controlled study we investigated the effect of a single intranasal dose of oxytocin on judgements of facial trustworthiness and attractiveness. We found that oxytocin administration increased ratings of trustworthiness and attractiveness of male and female targets in raters of both sexes relative to control ratings, suggesting that higher levels of this neuropeptide may enhance affiliative behaviour towards unfamiliar others. Our results provide evidence in support of a general facilitative role of oxytocin in promoting positive trait judgements.