Evidence-based cognitive behavioral therapy for eating disorders includes a component of exposure therapy, which involves patients confronting feared eating and body-related stimuli while preventing safety behaviors. With recent research demonstrating that eating-related fears and safety behaviors are central to eating disorder pathology, there is increased emphasis on improving the efficacy of exposure therapy in eating disorders. Doing so will require a better understanding of important mechanisms of action in this treatment. The present study explored how changes during treatment in eating-related fears and avoidance as well as body-related safety behaviors influence overall treatment outcomes. Individuals with eating disorders (N = 71) receiving exposure-based treatment completed measures of global eating disorder severity at admission and discharge. Hypothesized mechanisms of action were also assessed at admission and discharge as well as at a 2-week time point after beginning treatment. Path modeling analyses showed that decreased eating-related cognitions (feared concerns about eating) and emotions (anxiety about eating) at the 2-week time point were prospectively predictive of lowered global eating disorder symptom severity at discharge. Additionally, reduced body checking and avoidance behaviors after 2 weeks of treatment were also associated with lower eating disorder severity at discharge. These findings highlight the importance of exposure-based therapy in eating disorders and the need to uniquely address eating-related fears and safety behaviors.