The processing of social stimuli generated by one's own voluntary behavior is an element of social adaptation. It is known that self-generated stimuli induce attenuated sensory experiences compared with externally generated stimuli. The present study aimed to examine this self-specific attenuation effect on early stimulus processing in the case of others' facial expressions during interpersonal interactions. In addition, this study explored the possibility that the self-specific attenuation effect on social cognition is modulated by antisocial personality traits such as Machiavellianism. We analyzed early components of the event-related brain potential in participants elicited by happy and sad facial expressions of others when the participant's decision was responsible for the others' emotions and when the others' facial expressions were independent of the participant's decision. Compared to the non-responsible condition, the responsible condition showed an attenuated amplitude of the N170 component in response to sad faces. Moreover, Machiavellianism explained individual differences in the self-specific attenuation effect depending on the affective valence of social signals. The present findings support the possibility that the self-specific attenuation effect extends to interpersonal interactions and imply that distorted cognition of others' emotions caused by one's own behavior is associated with personality disorders that promote antisocial behaviors.