Crowding at destinations is becoming an important issue in sustainable tourism. This study examines the relationship between tourist perceptions of crowding, environmentally responsible behavior (ERB), and intention to recommend a destination, from a helping behavior perspective. It proposes two discrete emotions, in particular anger and sympathy, to understand how tourist perceptions of crowding affect their helping behavior. We collected data through an online survey of tourists who had visited Jeju Island, which has emerged as Korea's tourism hub. We performed structural equation modeling (SEM) and regression analysis to empirically test the research model. The results reveal that while tourist perceptions of spatial crowding positively impact both anger and sympathy, human crowding perceptions do not link to them. Further, we investigated the incompatible roles of anger and sympathy in tourist ERB and intention to recommend. Whereas anger weakens tourist ERB and intention to recommend, sympathy may strengthen them. This study also examined whether destination social responsibility (DSR) moderates the impact of crowding perceptions on the aforementioned emotions. In addition to encouraging relevant studies, we emphasize the importance of DSR, given the need for destination management organizations and tourism managers to understand tourists' emotional responses and helping behavior at crowded destinations.Sustainability 2020, 12, 2358 2 of 15 well established in tourism literature that crowding perceptions may relate to tourism impacts [10,11]. While it is well known that tourism impact may negatively contribute to tourist ERB [8], the influence of crowding perceptions on tourist ERB has been neglected. Specifically, the possible positive role of crowding perceptions on ERB remains unknown. Moreover, although crowding has been considered to negatively affect tourist experience, empirical evidence shows that the relationship between crowding and word of mouth (WOM) is not always negative [12]. Hence, this study's key research objective is to investigate how tourists' crowding perceptions can serve as an ambivalent role to strengthen (and weaken) their ERB and intention to recommend in terms of helping behavior. ERB can be viewed as a form of helpful behavior to support the destination environment. We also expect that recommending a destination to others will be helpful in destination management organization [9].To this end, we emphasize the distinct role of two discrete emotions-anger and sympathy-in the relationship between crowding perceptions and tourists' helping behavior, based on the stimulus-organism-response (SOR) framework [13]. Environmental psychology considers crowding to be a form of environmental stimulus [14], which, in turn, promotes an internal state (i.e., emotions) and behavior. While both anger and sympathy are likely to be experienced in harmful situations, they are different in that sympathy is elicited by patients who need help, while anger is usually experienced as blaming of specific ag...