Objectives: To determine the role of elevated serum bilirubin in the diagnosis of acute appendicitis. Methods: The study conducted in the period from January to July 2008 included 58 patients admitted to surgical department at Prince Rashed Bin Al–Hassan Hospital with clinical diagnosis of acute appendicitis. Preoperatively patient’s blood was collected for serum bilirubin. The study divided postoperatively into two study groups: Group I: 22 (37.9%) with acute appendicitis (males: 19 and females: 3. and their age ranged from 12 to 36 years), Group II: 36 (62.1%) without acute appendicitis (males: 32 and females: 4. and their age ranged from 14 to 38 years). Receiver Operating Characteristic (ROC) curve analysis used to find the best total bilirubin cutoff value for discrimination of acute appendicitis. Results: Total serum bilirubin among patient with acute appendicitis (6.83 ± 2.9 mg/dL) was statistically higher than patient without acute appendicitis (0.78 ± 0.67 mg/dL) P–value < 0.0001. The total serum bilirubin cutoff value > 1.69 mg/dL showed sensitivity 100% (95% CI, 84.4–100%) and specificity 91.67% (95% CI, 77.5–98.2%). Conclusion: Elevated total serum bilirubin is a good indicator and a new diagnostic tool for acute appendicitis.