This study examined the moderated-moderated mediating effect of negative urgency and positive emotion on the relationship between stress and non-suicidal self-injury through negative emotion. Self-reported data from 392 Korean undergraduate students were analyzed. The moderated-moderated mediating effects of negative urgency and positive emotion were significant. In other words, undergraduate students experience negative emotions when exposed to stressful events, and the possibility of self-injury increases for students who have high negative urgency and who do not experience positive emotions in daily life. Such results highlight that in order to prevent undergraduates from hurting themselves it is important to consider behavioral impulsivity related to negative emotions, as well as the level of positive emotions and negative emotions. Based on these findings, intervention strategies for undergraduate students' self-injuries are discussed.