Background: Abdominal pain constitutes the most common complaint for geriatric patients who present to the emergency department, with nearly 20% suffering from acute appendicitis (AA). Although key for diagnosis, clinical symptoms tend to be weak and atypical in the elderly. Therefore, patients present late to health institutions. Hence, prognosis and complication rates are worse in the elderly. Here, we aimed to reveal the role of basic laboratory parameters in diagnosing AA and determining disease severity. Methods: 143 elderly patients who underwent appendectomy were retrospectively analyzed. The patients were divided into three groups based on AA severity as Group I: negative appendectomy (n=15); Group IIa: uncomplicated appendicitis (n=79); Group IIb: complicated appendicitis (n=49). Results: We found no difference between the groups for age, sex, or comorbid diseases (p>0.05). As the time of admission to the hospital increases, the severity of the disease increases. Group IIb had higher length of stay and complication rates (p<.0.05) Conclusions: Preoperative WBC, neutrophil, NLR, MPV, CRP, and direct and total bilirubin levels can be used as biomarkers to determine AA diagnosis in the elderly. NLR, PLR, RDW, CRP, and direct and total bilirubin levels can be used to determine the presence of complications in appendicitis.