This research aimed to examine the effect of emotional dissonance and emotional intelligence on the prosocial behavior of fashion salespeople in department stores, and whether emotional intelligence mediates the relationship between emotional dissonance and prosocial behavior. Moreover, we aimed to suggest a method to improve the prosocial behavior of salespeople as a strategy to obtain a continuous competitive advantage in an increasingly competitive fashion distribution environment. This research was conducted through a questionnaire survey, and 345 responses were collected from department store salespeople for the final analysis. First, the analysis results showed that the emotional dissonance of salespeople arose from their dealings with their organization and with customers. Prosocial behavior was deduced to be a factor of the cooperation with coworker and extra-role customer service. The emotional intelligence was deduced to be a factor of the use of emotion, regulation of emotion, self-emotion appraisal, and others´emotion appraisal. Second, with a higher level of emotional dissonance against the organization, there was less cooperation with coworker, while a higher emotional dissonance against customers resulted in increased cooperation with coworker. Third, it appeared that with a higher level of emotional dissonance against the organization, there was a higher utilization of use of emotion, self-emotion appraisal, and others´emotion appraisal of emotional intelligence. Fourth, as the regulation of emotion, self-emotion appraisal, and use of emotion were higher, there was more cooperation with coworker, whereas an increase in the utilization of one`s own emotion and emotional control resulted in a higher level of extra-role customer service. Finally, emotional intelligence has a significant mediating effect between emotional dissonance and prosocial behavior. The above results suggest that for department stores to improve the prosocial behavior of their sales staff requires the establishment of a method to enhance the emotional intelligence of the staff. The results also indicate that there is a need for department stores to prepare a systemic tool to enable them to select people with a high degree of emotional intelligence when recruiting salespeople.