BACKGROUND Renal dysfunction is a leading cause of death in patients with acute pancreatitis (AP) and often occurs later than respiratory complications. Whether respiratory complications can predict renal impairment remains unclear. The aim of this study was to investigate the association between pleural effusion and renal dysfunction in AP. MATERIAL AND METHODS Medical records were reviewed from individuals who were hospitalized with AP from January 1, 2015 to December 31, 2019. The patients were divided into 2 groups, based on the presence or absence of pleural effusion on admission. Disease severity, renal function parameters, and outcomes were compared between the 2 groups. RESULTS A total of 222 patients were enrolled, 25 of whom had pleural effusion on admission and 197 who did not. Patients with AP who had pleural effusion had more serious illness (higher incidences of pancreatic inflammation, pancreatic fluid collection, and moderate-to-severe AP; worse Bedside Index for Severity in Acute Pancreatitis score; and a higher modified computed tomography severity index [all P<0.05]) plus worse outcomes (higher incidences of ventilation and vasopressor use [both P<0.05]). Moreover, patients with pleural effusion had a higher level of blood urea nitrogen and lower estimated glomerular filtration rate (both P<0.05). After adjustment for potential confounders, pleural effusion was a risk factor for renal failure in patients with AP (odds ratio 6.32, 95% confidence interval 1.08-36.78, P=0.040). CONCLUSIONS Pleural effusion is associated with severe renal dysfunction in AP. Therefore, efforts should be made to improve early recognition and timely treatment of renal failure by closely monitoring renal function in patients with AP and pleural effusion on admission.