Empathy deficiency is considered a cardinal trait associated with psychopathy. This study examined empathy as cognitive and affective constructs during a mood task meant to evoke happiness and sadness. Fifty-two undergraduate students organized in same-gender pairs (17 female pairs and 9 male pairs) completed measures of empathy, psychopathy, social desirability, social anxiety, demographics and health. Participants engaged in a social mood task where one individual spoke about happy or sad events in the past year while the other individual listened. The procedure incorporated a within-subjects design, so that the participant order switched so each participant would listen and speak about both happy and sad events. Throughout the procedure, cardiac measures were collected through an electrode strap. Psychopathic traits was related to reductions in heart rate variability when listening to other participants discuss sad events, and this was most pronounced in those who also had low empathy scores. Trait cognitive empathy was unrelated to cardiac changes or to state cognitive empathy. Participants' own heart rate and heart rate variability were the only predictors of heart rate and heart rate variability during the mood induction procedures, while the other participant's heart rate and heart rate variability were not. Additionally, psychopathic traits did not moderate this relationship. Results are discussed in terms of how vagal withdrawal may be related to psychopathy and low empathy, especially when listening to sad events.