Despite the emphasis on the role of emotion dysregulation in deliberate self-harm (DSH), no studies have examined this association among patients with substance use disorders (SUD). This study examined if emotion dysregulation is heightened among SUD inpatients with (vs. without) DSH, and if the association between DSH and emotion dysregulation remains significant when controlling for their shared association with risk factors for both, including borderline personality disorder (BPD), posttraumatic stress disorder (PTSD), childhood abuse, and substance use severity. Findings indicate heightened emotion dysregulation among SUD patients with (vs. without) DSH, and provide evidence of a unique association between emotion dysregulation and DSH when controlling for BPD, PTSD, childhood abuse, and substance use severity. Findings also highlight the particular relevance of three dimensions of emotion dysregulation to DSH among SUD patients: limited access to effective emotion regulation strategies, difficulties engaging in goal-directed behaviors when distressed, and emotional nonacceptance.