Background and aims The 30-day readmission rate is a nationally recognized quality measure with nearly one-fifth of patients being readmitted. This study aims to evaluate frailty, as measured by the hospital frailty risk score (HFRS), as a prognostic indicator for 30-day readmission after inpatient ERCP.Methods We analyzed weighted discharge records from the 2017 Nationwide Readmissions Database (NRD) to identify patients undergoing ERCP between 01/01/2017 and 11/30/2017. Our primary outcome was the 30-day unplanned readmission rate in frail (defined as HFRS > 5) against non-frail (HFRS < 5) patients. A mixed effects multivariable logistic regression method was employed.Results Among 68,206 weighted hospitalized patients undergoing ERCP, 31.3% were frail. Frailty was associated with higher 30-day readmission (OR 1.23, 95% CI [1.16-1.30]). Multivariable analysis showed a greater risk of readmission with cirrhosis (OR 1.26, 95% CI [1.10-1.45]), liver transplantation (OR 1.36, 95% CI [1.08-1.71]), cancer (OR 1.58, 95% CI [1.48-1.69]), and male gender (OR 1.24, 95% CI [1.18-1.31]). Frail patients also had higher mortality rate (1.8% vs 0.6%, p < 0.01)], longer LOS during readmission (6.7 vs 5.6 days, p < 0.01), and incurred more charges from both hospitalizations ($175,620 vs $132,519, p < 0.01). Sepsis was the most common primary indication for both frail and non-frail readmissions but accounted for a greater percentage of frail readmissions (17.9% vs 12.4%, p < 0.01).Conclusions Frailty is associated with higher readmission rates, mortality, LOS, and hospital charges for admitted patients undergoing ERCP. Sepsis is the leading cause for readmission. Independent risk factors for readmission include liver transplantation, cancer, cirrhosis, and male gender.