The present research investigated first the facial feedback measured by EMG (electromyography) during decisions to engage in prosocial-helping behaviors and secondly the relation between this psychophysiological correlate and emotional empathy trait in young people. Thirty young subjects were invited to choose to adopt or not a prosocial behavior in response to social interactions. An increased zygomatic and corrugator muscle activity was found in response to prosocial interventions. Moreover, a significant positive correlation was found between empathic profile and the EMG modulation. These results highlight the role of emotions and empathy in prosocial behavior, induced by an "emotional contagion effect."