<p>Women with substance use disorders (SUD) face persistent inequities in access to and engagement with treatment, shaped by the intersection of gender, trauma, and structural conditions. This systematic review synthesizes empirical evidence on barriers to treatment access among women with SUD and identifies key components of gender-responsive and trauma-informed interventions. Following PRISMA 2020 guidelines, systematic searches were conducted in Web of Science, PubMed, and Scopus for empirical studies published from 1 January 2015 to 31 December 2025. Fifteen empirical studies conducted in Western contexts met inclusion criteria. Data were extracted using a PICO framework, synthesized through thematic and structured narrative synthesis, and appraised using design-specific CASP checklists. Four interrelated barrier domains were identified: structural, sociocultural, normative, and emotional. Facilitating factors included trauma-informed care, integrated and flexible services, mother–child programs, and empathetic therapeutic relationships, which were reported as supporting engagement, perceived safety, and continuity of care. Barriers to addiction treatment for women are systemic rather than individual, underscoring the need for gender-responsive and trauma-informed models to achieve equitable and effective care.</p>