The purpose of this study was to examine the predictive validity of the Eating Disorder Recovery Self-Efficacy Questionnaire (EDRSQ), an empirically-derived self-report instrument that assesses confidence to eat without engaging in eating disordered behavior or experiencing undue emotional distress (Normative Eating Self-Efficacy) and confidence to maintain a realistic body image that is not dominated by pursuit of thinness (Body Image Self-Efficacy). Participants were 104 female inpatients with anorexia nervosa (AN), subthreshold AN, or underweight bulimia nervosa who were treated at a specialized eating disorder clinic and completed the EDRSQ and Eating Disorder Inventory-2 (EDI-2) Drive for Thinness (DT) and Body Dissatisfaction (BD) subscales upon admission. A subset of patients completed the EDRSQ (n=81) and EDI-2 subscales (n=70) following inpatient treatment. Self-efficacy increased significantly during treatment. EDRSQ scores at admission were inversely related to length of hospital stay and posttreatment DT and BD subscales and positively related to partial hospital weight gain rate. The EDRSQ significantly predicted length of hospital stay and posttreatment BD above and beyond clinical indicators and eating disorder psychopathology at inpatient admission. Findings support the validity of the EDRSQ and suggest it is a useful predictor of short-term hospital treatment outcome in underweight eating disorder patients.