Acute necrotizing pancreatitis (ANP) can result in a significant healthcare burden. The present study aimed to develop a new scoring system to accurately and promptly identify patients with a high likelihood of mortality to determine the need for aggressive measures.We retrospectively analyzed patients diagnosed with ANP using the National Inpatient Sample (NIS). The mortality in ANP during admission (MANP-A) scoring system was derived using multivariate Cox regression analysis and validated using receiver operating characteristic (ROC) curves in a validation cohort.A total of 22,980 hospitalizations were identified in the derivation cohort. There was a predominance of males (65%) and white race (73%). Five variables showed significant association with mortality and were selected for developing the MANP-A scoring system: age ≥60 years; acute renal failure/kidney injury; sepsis with shock; vasopressor use; and disseminated intravascular coagulation. The MANP-A score has a maximum of 5 points and the cutoff for predicting mortality was set at 2 points. The area under the curve (AUC) using the ROC curve of the derivation cohort was 0.9195, 95% confidence interval [CI] 0.8838-0.9551 (P<0.001) for 7- and 0.8954, 95%CI 0.8723-0.9185 (P<0.001) for 30-day periods. The AUC of the Validation Cohort was 0.9204, 95%CI 0.8937-0.9469 (P<0.001) for 7- and 0.9059, 95%CI 0.8893-0.9223 (P<0.001) for 30-day periods.We propose a simple and objective score for predicting ANP inpatient mortality at 7- and 30-day intervals with high validity.