Objective: Internalized weight bias is experienced by young women across the weight spectrum and contributes to the development of eating disorders. Interventions have demonstrated preliminary success in reducing weight self-stigma and disordered eating, but findings have only applied to individuals with overweight and obesity and little is known about the mechanisms of change. A mediation model was developed to show how interventions for internalized weight bias indirectly improve eating behaviors by reducing drive for thinness and body image avoidance. Support for the model was obtained in a cross-sectional pilot study. Informed by the mediation model, a three-session cognitive-behavioral group program was developed to increase the potency of treatment for internalized weight bias. The following three studies examined the mediation model and group program among racially and ethnically diverse undergraduate women with wide-ranging body sizes. Method: Study 1 ("N" = 179) was a cross-sectional study designed to replicate the pilot study and provide additional support for the theoretical model underlying the group program. Study 2 ("N" = 5) was a pilot intervention to examine the feasibility and acceptability of the treatment in a single group of undergraduate women. Study 3 ("N" = 55) was a randomized controlled trial (active vs. waitlist control) that evaluated the feasibility, acceptability, and effectiveness of the program in improving internalized weight bias, disordered eating, drive for thinness, body image avoidance, body dissatisfaction, body acceptance, thin ideal internalization, and general distress. Participants completed measures at baseline, post-treatment, and six-week follow-up. Results: Study 1 confirmed mediation of the relationship between internalized weight bias and disordered eating by drive for thinness and body image avoidance. Treatment adherence and group leader competence were high in Study 2 and Study 3. The program was well-received, as evidenced by high rates of attendance and retention. Feedback from participants indicated that the program was informative, acceptable, and impactful. Participants in the active condition reported improvement on all outcomes relative to the waitlist control condition. Within the combined sample, there was clinically meaningful improvement on internalized weight bias, disordered eating, drive for thinness, body image avoidance, body dissatisfaction, body acceptance, thin ideal internalization, and general distress from baseline to post-treatment. Despite some rebound in body image avoidance, significant improvement remained in all outcomes at follow-up. Discussion: The current research revealed how interventions for internalized weight bias may indirectly improve eating disturbances. Results also showed that a brief cognitive-behavioral group program was feasible, acceptable, and effective in improving internalized weight bias, eating disturbances, and other psychological outcomes among undergraduate women. Findings demonstrated that women with diverse cultural backgrounds and body sizes ranging from healthy to obese benefitted from a weight self-stigma reduction intervention. If the observed improvements were sustained over time, additional benefits could emerge, such as the reduced incidence of eating disorders. [The dissertation citations contained here are published with the permission of ProQuest LLC. Further reproduction is prohibited without permission. Copies of dissertations may be obtained by Telephone (800) 1-800-521-0600. Web page: http://bibliotheek.ehb.be:2222/en-US/products/dissertations/individuals.shtml.]