Young adult women from an ongoing community cohort study with past year self- injurious thoughts completed a 21 day ecological momentary assessment protocol. The study used multilevel path analyses to model within-person effects of negative affect and interpersonal stress on subsequent suicide and NSSI urges within several hours. The study found that when modeled simultaneously, within person changes in internalizing, but not externalizing, negative affect predicted later self-injurious urges. Rejection and criticism predicted later self-injurious urges, with rejection showing a unique relationship to NSSI urges specifically. The effects of rejection and criticism on later NSSI and suicide urges were mediated by internalizing negative affect; rejection also retained a significant direct effect on NSSI urges. The study concluded that interpersonal stressors may be potent near-term risk factors for self-injurious urges by increasing internalizing negative affect among vulnerable individuals. The direct role of rejection and criticism on self-injurious urges is less clear, particularly for suicide. These findings have implications for understanding processes underlying self-injurious urges, as well as designing real-time interventions for these experiences in daily life.