Deliberate self-harm (DSH) is a clinically important behavior commonly associated with borderline personality disorder (BPD). Despite the clinical relevance and associated negative consequences of this behavior, however, there are few empirically supported treatments for DSH among individuals with BPD, and those that exist are difficult to implement in many clinical settings (due to their duration and intensity). To address this limitation, Gratz and Gunderson (2006) examined the efficacy of a 14-week, adjunctive emotion regulation group therapy (ERGT) for DSH among women with BPD. Although the results of this initial trial were promising (indicating positive effects of this treatment on DSH, emotion dysregulation, experiential avoidance, and psychiatric symptoms), they require replication and extension. Thus, the purpose of this study was to further develop this ERGT by examining its utility across other settings, a more diverse group of patients, a wider range of outcomes, and group leaders other than the principal investigator. Twenty-three women received this ERGT in addition to their ongoing treatment in the community. Self-report and interview-based measures of DSH and other self-destructive behaviors, psychiatric symptoms, adaptive functioning (including social and vocational impairment and quality of life), and the proposed mechanisms of change (emotion dysregulation and experiential avoidance) were administered pre- and posttreatment. Results indicate significant changes over time (accompanied by large effect sizes) on all outcome measures except quality of life and self-destructive behaviors (although the latter was a large-sized effect). Further, 55% of participants reported abstinence from DSH during the last two months of the group.