The aim of the present study was to investigate sex-related variations in the perception of the duration of emotional stimuli (human faces). Twenty male and 20 female participants estimated the duration of angry, ashamed and neutral faces marking 0.4 to 1.6 s intervals. Female faces were used in one session, and male faces in the other. Compared to the angry faces condition, intervals were underestimated when ashamed faces were shown. However, the intervals in neither conditions were significantly overestimated or underestimated compared to the neutral condition. Even more critical is the fact that there was an underestimation by male participants of the duration of male faces compared to female faces; and female participants overestimated the duration in the anger condition, compared with the shame condition, only when male faces were presented. Moreover, the emotional effects on the participants’ performance were correlated to inter-individual differences in empathic abilities. The findings are discussed in terms of sex differences, of social context, and of how attention is solicited and arousal generated by emotions.