Background Readmission after hospital discharge is common in adolescents with eating disorders. Studies on the association between rapidity of weight gain and readmission are inconsistent. With an emphasis on more rapid weight gain during hospitalization, the effect of this strategy on readmission rates warrants further investigation. Objective This project explored the relationship between rate of weight gain during hospitalization and medically necessitated readmissions. Subjects Eighty-two patients who: were admitted due to an eating disorder during a 5-year period; achieved weight restoration to ≥84% of ideal body weight (IBW); had a follow-up visit with the adolescent medicine service after discharge; and, had information available on rate of weight gain. Methods Data were extracted from medical records. Multiple logistic regression was used to analyze the effect of rate of weight gain on readmission. The effect of a comorbid psychiatric diagnosis was tested for an interaction. Results Of patients 20.7% required readmission. The median rate of weight gain was 118.6 g/day [interquartile range (IQR) = 91.8-150.8]. There was a 1.8 times [95% confidence interval (CI) = 0.9-3.6, p = 0.087] greater odds of readmission with each increase in weight gain quartile after adjusting for potential confounders. Patients in the lowest rate of weight gain quartile and no psychiatric co-morbidity had a significantly lower predicted probability of readmission (25.1%) compared to those with a psychiatric comorbidity and in the highest quartile of rate of weight gain (48.4%). Conclusion Patients with eating disorders who have rapid inpatient weight gain and psychiatric co-morbidities may be at increased risk for readmission.