Background: Appendicitis is the most common acute abdominal condition requiring emergency surgery, with a lifetime risk of 6%. Appendectomy continues to be one of the commonest procedures in general surgery, accounts for approximately 1% of all surgical operation. Despite the increased use of ultrasonography, computed tomography scanning and laparoscopy, the rate of misdiagnosis of appendicitis has remained constant (15.3%). The aim of this study was to whether Serum Bilirubin can be considered as a new laboratory marker to aid in the diagnosis of acute appendicitis and if so, does it have the predictive capacity to warn us about complicated appendicitis.Methods: This was prospective observational study done in Mahatma Gandhi Medical College and Research Institute, Pondicherry between November 2014 and August 2016. About 110 patients of acute appendicitis who had undergone appendicectomy were studied. Data was collected and analyzed critically.Results: Males 66 (60%) outnumbered females 44 (40%) and overall mean age was 26.61±12.37 years. Of the 110 patients, 9% were normal appendix, 59.09% were confirmed as acute appendicitis while 31.81% were diagnosed with complicated appendicitis on biopsy. The Sensitivity and Specificity of serum bilirubin as a marker in predicting Acute appendicitis and complicated appendicitis was 47.6% and 90.9% respectively. Similarly, the Positive predicative value and Negative predicative value for the same was 88.5% and 61.5% respectively with odds ratio 12.4 with significant p value <0.0001.Conclusions: Serum bilirubin is easily available test and cheap and can be estimated from the sample of blood drawn for routine blood investigations. Patients with clinical signs and symptoms of appendicitis and with hyperbilirubinemia should be identified as having a higher probability of complicated appendicitis. Hence, serum bilirubin levels have a predictive potential for the diagnosis of severity of acute appendicitis and need for early appendicectomy. If total serum bilirubin is added to already existing laboratory tests, then the diagnosis of complicated appendicitis in clinically suspected cases can be made with fair degree of accuracy, the need for CECT and MRI can be reduced and unnecessary delay in appendicectomy can be avoided.