Typically-developing (TD) adults detect angry faces more efficiently within a crowd than non-threatening faces. Prior studies of this social threat superiority effect (TSE) in ASD using tasks consisting of schematic faces and homogeneous crowds have produced mixed results. Here, we employ a more ecologically-valid test of the social TSE and find evidence of a reduced social TSE in adults with ASD (n = 21) relative to TD controls (n = 28). Unlike TD participants, the ASD group failed to show the normative advantage for detecting angry faces faster than happy faces, either within crowds of neutral or emotional faces. These findings parallel prior work indicating a reduced sensitivity in ASD to facial cues of untrustworthiness, and may reflect a vulnerability for evaluating social harm.