When we see new people we rapidly form first impressions. While past research has mostly focused on the role of morphological or emotional cues, we here ask whether the visceral states of the perceiver bias first impressions. Across 3 studies we investigated how “gut feelings”, driven by the interoceptive impact of cardiac signals, may influence the perceived trustworthiness of faces. Faces presented in synchrony with the participants’ cardiac systole were chosen less often as more trustworthy than those presented out-of-synchrony. Faces presented in synchrony cardiac systole were also explicitly judged as less trustworthy. Finally, the presentation of faces in synchrony with the participants’ cardiac diastole did not modulate perceived trustworthiness, suggesting that the systolic phase is necessary for such ‘gut feelings’. These findings highlight the role of phasic interoceptive information in the processing of social information and provide a mechanistic account of the role of visceroception for social perception.