Altered visual perception has been observed across all phases of psychotic illness, suggesting that perceptual measures might be useful in identifying people at clinical high risk for psychosis (CHR). In a preliminary study, we found that CHR participants reported perceiving more faces in binarized human portraits on the Mooney Faces Test (MFT). Here, we aimed to replicate these findings and extend understanding of underlying processes and clinical correlates of MFT performance in the Computerized Assessment of Psychosis Risk (CAPR) cohort: CHR (n = 159), help-seeking psychiatric controls (n = 130), and healthy controls (n = 86). The MFT was adapted to include three image conditions (upright, inverted, and scrambled), and included follow-up questions regarding the physical characteristics of the faces that participants reported perceiving, to verify accuracy of perception and assess response bias. The CHR group reported more faces than both control groups in the inverted and scrambled conditions. In addition, the CHR group was as accurate at judging the age and gender of faces as the other groups. Among CHR participants, increased reporting of faces in the inverted condition was significantly correlated with more severe positive symptoms and poorer role functioning. We discuss the findings in terms of multiple perspectives, including changes in perceptual sensitivity, predictive coding, and perceptual organization.