Background: Moderately severe acute pancreatitis (MSAP) and severe acute pancreatitis (SAP) are associated with organ failure (OF), which can be lethal. Aims: This study determined the factors that predict the severity of AP at admission in elderly patients. Methods: In this retrospective study, the data from elderly patients (> 60 years of age) admitted within 72 h of onset of symptoms without OF were collected. These data at admission were analyzed and correlated with the severity of AP. To identify the factors associated with more serious AP (i.e. MSAP and SAP), patients were divided into mild acute pancreatitis (MAP) and MSAP + SAP groups. Results: A total of 198 patients [MAP group (n = 135) and MSAP + SAP group (n = 63)] were included. Biliary disease was the most common etiology. Respiratory failure was the most common OF. Logistic regression analyses indicated that idiopathic etiology (odds ratio [OR]: 3.029, 95% confidence interval [CI]: 1.017–9.022, p = 0.047), pre-existing pulmonary disease (OR: 7.104, CI 1.750–28.84, p = 0.006), increased hematocrit level (OR: 3.717, 95%CI 1.372–10.070, p = 0.010), serum calcium (OR: 0.023, 95%CI 0.001–0.371, p = 0.008), serum glucose (OR: 1.157, 95%CI 1.031–1.299, p = 0.013), arterial partial pressure of oxygen (PaO2) (OR: 0.914, 95%CI 0.874–0.956, p < 0.001), and pleural effusion (OR: 4.979, 95%CI 1.863–13.303, p = 0.001) were independent predictors of more serious AP. Conclusion: This study found that idiopathic etiology, pre-existing pulmonary diseases, increased hematocrit level or pleural effusion, higher serum glucose, and lower serum calcium or PaO2 at the time of admission independently correlated with more serious AP in the elderly patients. © 2020, Springer Nature Switzerland AG.