In everyday life, other peoples' distress is sometimes genuine (e.g., real sadness) and sometimes pretended (e.g., feigned sadness aimed at manipulating others). Here, we present the first study of how psychopathic traits affect responses to genuine versus posed distress. Using facial expression stimuli and testing individual differences across the general population (N = 140), we focus on the affective features of psychopathy (e.g., callousness, poor empathy, shallow affect). Results show that although individuals low on affective psychopathy report greater arousal and intent to help toward faces displaying genuine relative to posed distress, these differences weakened or disappeared with higher levels of affective psychopathy. Strikingly, a key theoretical prediction-that arousal should mediate the association between affective psychopathy and intent to help-was supported only for genuine distress and not for posed distress. A further novel finding was of reduced ability to discriminate the authenticity of distress expressions with higher affective psychopathy, which, in addition to and independently of arousal, also mediated the association between affective psychopathy and reduced prosociality. All effects were specific to distress emotions (did not extend to happiness, anger, or disgust), and to affective psychopathy (did not extend to Factor 2 psychopathy, disinhibition, or boldness). Overall, our findings are highly consistent with Blair's theorizing that atypical processing of distress emotions plays a key etiological role in the affective aspects of psychopathy. We go beyond these ideas to add novel evidence that unwillingness to help others is also associated with a failure to fully appreciate the authenticity of their distress. (PsycINFO Database Record (c) 2019 APA, all rights reserved).