Objective: Elucidation of clinically relevant subtypes has been proposed as a means of advancing treatment research, but classifying anorexia nervosa (AN) patients into restricting and binge-eating/purging types has demonstrated limited predictive validity. This study aimed to evaluate whether an approach to classifying eating disorder patients on the basis of comorbid personality psychopathology has utility in predicting treatment response and readmission in patients with AN. Method: Data were collected from 154 AN patients (M [SD] age = 25.6[9.4] years; 95.5% female; 96.8% Caucasian) at admission, discharge, and 3 months postdischarge from intensive treatment. Latent profile analysis of personality traits assessed at admission was performed to classify participants into personality subtypes, which were then used to predict outcomes at discharge and risk of readmission. Results: The best fitting model identified 3 personality subtypes (undercontrolled, overcontrolled, low psychopathology) that contributed significantly to multivariate models predicting study outcomes. Undercontrolled patients were more likely to have a poor outcome at discharge than overcontrolled (OR = 3.56, p = 0.01) and low psychopathology patients (OR = 11.23, p less than 0.001). Undercontrolled patients also had a greater risk of discharge against medical advice (HR = 2.08, p = 0.02) and readmission than overcontrolled patients (HR = 3.76, p = 0.009). Binge-eating/purging versus restricting subtypes did not predict discharge against medical advice or readmission in the multivariate models. Conclusions: Findings support the clinical utility of personality subtypes in AN. Future work is needed to identify mechanisms that explain diminished treatment response in undercontrolled patients and to develop interventions for this high-risk group. (Contains 6 footnotes, 2 tables, and 1 figure.)