Purpose: Incarcerated women serving life sentences are a growing subpopulation with multiple mental health needs. However, no existing interventions have been designed for or tested with this population. Method: This study tested a gender-responsive, trauma-informed intervention (Beyond Violence) and examined changes in incarcerated women’s mental health and anger expression. Pre-, post-, and follow-up surveys were administered to two treatment groups with women with life sentences. Multilevel modeling was conducted to assess changes over time for women’s mental health and anger expression and to compare outcomes for women based on time served. Results: Significant positive outcomes were found for all women for some anger measures, and women who had been in prison for less than 10 years started with higher scores on multiple measures and showed significant changes over time. Discussion: This study offers insight into social work practice, policy advocacy, and research for this population of women.