BACKGROUND&OBJECTIVE: Acute appendicitis is a frequent surgical emergency and the more objective data the less unnecessary operations. The aim of this study is to evaluate the role of red cell distribution width (RDW) in the diagnosis of acute appendicitis. MATERIAL&METHODS: This retrospective study was conducted in a tertiary clinical setting. Patients underwent acute appendectomy between January 1^st, 2012 and December 31^st, 2013 were scanned from hospital database. Demographics, ultrasound reports, pathology reports, and RDW as well as biochemical results were recorded from patient charts. Data were recorded by principal investigators and then checked by two blinded researchers for accuracy. RESULTS: A total of 1502 subjects (n=744 for appendicitis and n=758 for control group) were included in the study. RDW levels were different between appendicitis and control groups (13.99 ± 1.86 vs. 12.62 ± 1.4, respectively) (p<0.001). Area under the curve for RDW was 0.779. White blood cell count and neutrophil counts were higher in appendicitis group. However, mean platelets volume and lymphocyte counts were higher in control group. CONCLUSION: We concluded that RDW can be a good indicator in the diagnosis of acute appendicitis but it must be combined with a detailed clinical assessment.