OBJECTIVE: Alcohol use is an important, but understudied, risk factor for nonsuicidal self-injury (NSSI), defined as deliberate physical harm to oneself without intent to die. Alcohol use may facilitate engagement in NSSI by increasing impulsivity and physical pain tolerance. Limited data also suggest that people engage in more medically severe NSSI under the influence of alcohol. METHOD: This secondary analysis study examined the use of alcohol prior to NSSI in a sample of 79 female patients with borderline personality disorder who were enrolled in a randomized clinical trial of dialectical behavior therapy. We used multilevel modeling (MLM) to examine preregistered hypotheses that alcohol use prior to NSSI would be related to the impulsivity of NSSI, physical pain experienced during NSSI, and the medical severity of injuries from NSSI. RESULTS: Participants endorsed alcohol use prior to 21.96% (47/221) of NSSI episodes, and roughly one third of participants ( CONCLUSIONS: Findings need to be replicated but indicate that alcohol use occurs frequently prior to NSSI and could be a target for reducing impulsive episodes of NSSI. (PsycInfo Database Record (c) 2025 APA, all rights reserved).