OBJECTIVE Treatment engagement rates are low for individuals with comorbid posttraumatic stress disorder (PTSD) and alcohol use disorders across available interventions and treatment modalities. A better understanding of who does and does not engage in treatment can help improve retention, completion, and subsequent treatment outcomes. METHODS Forty female survivors of intimate partner violence with PTSD and alcohol use disorder participated in a randomized controlled trial comparing twenty-five 90-minute sessions of either modified Seeking Safety or Facilitated Twelve-Step in a community-based outpatient clinic. This study examined differences in demographics and pre-treatment PTSD symptoms and alcohol use between participants who engaged in treatment (attended ≥ 6 sessions, n = 18) and those who dropped out (n = 22). RESULTS There were no significant differences in PTSD or alcohol use disorder symptoms between treatment conditions. Women who engaged in therapy versus those who did not were significantly older (M = 46.2, SD = 9.14 vs. M = 38.95, SD = 10.49, respectively; p =.027), and had fewer dependents (M =.17, SD =.38, range = 0-1 vs. M =.95, SD = 1.66, range = 1-7, respectively; p =.046). Greater avoidance/numbing PTSD symptoms (OR = 1.13, p =.028, 95% CI [1.02-1.25]) and more years of heavy drinking (OR = 1.04, p =.03, 95% CI [1.00-1.07]) were also significantly associated with treatment engagement. CONCLUSIONS This study replicates previous findings suggesting a need for additional retention strategies for younger women with dependents in comorbid PTSD and alcohol use disorder treatment. This is an analysis of data collected as part of a clinical trial registered as NCT00607412, at www.clinicaltrials.gov.