Nonsuicidal self-injury (NSSI) is prevalent among young adults, and is associated with myriad negative outcomes, including heightened suicide risk. The defective self model of NSSI theorizes that individuals who are highly self-critical and who feel they are deserving of punishment are more likely to choose NSSI over other emotion regulation strategies. This empirically-supported model has a number of under-examined implications. Specifically, individuals who engage in NSSI may be more prone to experiencing self-conscious emotions in response to negative social feedback, and this may place individuals at heightened imminent risk for NSSI in everyday life. Few studies have examined self-conscious emotional reactivity to daily social stressors among those who engage in NSSI, and more work is needed to identify person-specific contexts that indicate elevated risk for NSSI. Therefore, the present study first examined whether individuals with a history of NSSI (vs. without) display greater self-conscious and negative emotional reactions to daily social stressors, as well as more dysfunctional features of these daily social stressors. Second, we examined whether within-person increases in these emotional reactions and social stressor features predict increased risk for NSSI urges and behaviors in daily life. Participants were 134 young adult women who reported recent, recurrent NSSI (n = 77) or no NSSI history (n = 57) recruited from a large university and its surrounding community. Participants completed baseline measures of socioemotional functioning and engaged in a two-week daily diary protocol during which they reported on daily social stressors and NSSI urges and behaviors. The NSSI (vs. no NSSI) group reported significantly greater self-conscious and negative emotional reactions to daily social stressors, and social stressors characterized by greater distress, conflict, and confusion. In the NSSI group, experiencing social stressors characterized by greater-than-usual distress was associated with same-day NSSI urges and behavior. Experiencing social stressors characterized by greater-than-usual confusion predicted same-day NSSI urges, whereas greater-than-usual conflict predicted same-day NSSI behavior. Experiencing greater-than-usual self-conscious and negative emotional reactions to these stressors predicted same-day NSSI urges and behavior. Findings from this study have important clinical implications for the prevention and treatment of NSSI.