Background: Acute appendicitis (AA) is a common disease that includes all age groups and both genders in societies and is one of the most common causes of acute abdomen. It is important to distinguish between complicated and non-complicated appendicitis before surgery. This study aims to determine laboratory parameters that can be used to determine whether the disease is complicated or non-complicated in patients admitted to the emergency department with AA., Methods: Female and male patients admitted to the Emergency General Surgery Department between May 2019 and November 2020 and diagnosed with appendicitis were included in the study. Demographic data (age, gender, and protocol numbers), complete blood counts (Delta neutrophil index [DNI], hemoglobin, monocyte, neutrophil, eosinophil, basophil, platelet, platelet distribution width, mean platelet volume, reticulocyte distribution width), biochemical parameters (amylase, direct bilirubin, indirect bilirubin, albumin, calcium, and lactate dehydrogenase), and examination information were obtained from the hospital automation system and recorded via SPSS software. Parameters of patients were divided into two groups as complicated and non-complicated appendicitis groups were compared., Results: White blood cell (WBC), monocyte, neutrophil, DNI, total bilirubin, and direct bilirubin values were found to be statisti-cally significantly higher in the complicated appendicitis group compared to the non-complicated appendicitis group (p-values; <0.001, 0.003, <0.001, <0.001 and 0.008, respectively)., Conclusion: DNI, bilirubin values, WBC, monocyte, neutrophil, and eosinophil can be used as laboratory parameters to distin-guish between complicated and non-complicated AA.