We examined the association between the therapeutic alliance and treatment outcomes among 223 women with posttraumatic stress disorder (PTSD) and substance use disorders who participated in a multisite clinical trial of group treatments for trauma and addictions in the United States throughout 2004 and 2005. General linear models indicated that women who received Seeking Safety, a cognitive-behavioral treatment, had significantly higher alliance ratings than those in Women's Health Education, a control group. Alliance was related to significant decreases in PTSD symptoms and higher attendance in both interventions. Alliance was not related to substance use outcomes. Implications and limitations of the findings are discussed.