More than 40 years of research have shown that people favor members of their ingroup in their impressions, attitudes, and behaviors. Here, we propose that people also form different mental images of minimal ingroup and outgroup members, and we test the hypothesis that differences in these mental images contribute to the well-established biases that arise from minimal group categorization. In Study 1, participants were assigned to 1 of 2 groups using a classic minimal group paradigm. Next, a reverse correlation image classification procedure was used to create visual renderings of ingroup and outgroup face representations. Subsequently, a 2nd sample naive to the face generation stage rated these faces on a series of trait dimensions. The results indicated that the ingroup face was significantly more likely than the outgroup face to elicit favorable impressions (e. g., trusting, caring, intelligent, attractive). Extending this finding, Study 2 revealed that ingroup face representations elicited more favorable implicitly measured attitudes than did outgroup representations, and Study 3 showed that ingroup faces were trusted more than outgroup faces during an economic game. Finally, Study 4 demonstrated that facial physiognomy associated with trustworthiness more closely resembled the facial structure of the average ingroup than outgroup face representation. Together, these studies suggest that minimal group distinctions can elicit different mental representations, and that this visual bias is sufficient to elicit ingroup favoritism in impressions, attitudes and behaviors.