Objective: Acute pancreatitis can cause local or systemic complications and has high morbidity and mortality rates. In the early stages of pancreatitis, a decrease in the barrier function of the intestines and an increase in bacterial translocation are observed. Zonulin is a marker used to evaluate the integrity of the intestinal mucosal barrier. We aimed to investigate whether measuring serum zonulin levels would contribute to the early prediction of complications and severity in acute pancreatitis. Materials and Methods: Our study was an observational, prospective study and included 58 patients with acute pancreatitis and 21 healthy controls. Causes of pancreatitis and serum zonulin levels of the patients at the time they were diagnosed with pancreatitis were recorded. The patients were evaluated in terms of pancreatitis severity, organ dysfunction, complications, sepsis, morbidity, length of hospital stay, and mortality Results: Zonulin levels were higher in the control group and lowest in the severe pancreatitis group. No significant difference was observed in zonulin levels according to disease severity. There was no signifi- cant difference between zonulin levels in patients who developed organ dysfunction or sepsis. In patients with acute pancreatitis complications, zonulin levels were found to be significantly lower with a mean of 8.6 ng/mL (P < .02). Conclusion: Zonulin levels are not a guide in the diagnosis of acute pancreatitis, in determining its severity, and in the development of sepsis and organ dysfunction. The zonulin level at the time of diagnosis may be helpful in predicting complicated acute pancreatitis. Zonulin levels are not effective in demonstrating necrosis or infected necrosis.