Background: The advantages of aggressive fluid treatment (AFT) compared to conservative fluid treatment (CFT) within 24 h for acute pancreatitis (AP) remain controversial in adult patients. A meta-analysis was undertaken to investigate whether aggressive strategies are more beneficial.Methods: We searched (on February 1, 2021) PubMed, Embase, and the Cochrane Library for eligible trials that assessed the two therapies and performed a meta-analysis. The primary endpoint was in-hospital mortality. Secondary outcomes were adverse events (e.g., renal failure and pancreatic necrosis) within 24 h of treatment.Results: Five randomized controlled trials (RCTs) and 8 observational studies involving 3,127 patients were identified. There was a significant difference in in-hospital mortality for AFT compared to CFT (OR, 1.66; P = 0.0001). The incidences of renal failure (OR, 2.38; P < 0.00001) and pancreatic necrosis (OR, 2.34; P < 0.0001) were similar and significantly different between the two groups. Patients aged > 50 years had a potentially higher utilization of mechanical ventilation and incidence of respiratory failure (OR, 4.88; P < 0.00001). Persistent organ failure, systemic inflammatory response syndrome (SIRS) and length of hospital stay did not differ significantly between the two groups. Sensitivity analysis identified two significant changes: one in persistent SIRS (OR, 2.37; P = 0.02) in patients aged > 50 years and one in the overall incidence of persistent organ failure (OR, 1.81; P = 0.02).Conclusions: Compared to CFT, AFT increases in-hospital mortality and the incidence of renal failure, pancreatic necrosis and respiratory failure with relatively strong evidence.