Background: Acute appendicitis is a common surgical emergency, and diagnosing complicated cases such as gangrenous or perforated appendicitis remains challenging. Hyperbilirubinemia has been proposed as a potential diagnostic marker to aid in identifying these severe cases. Aim: To evaluate the role of hyperbilirubinemia in predicting gangrenous or perforated appendicitis and assess its diagnostic accuracy. Methods: A prospective observational study was conducted at Chamarajanagara Institute of Medical Sciences, Karnataka, from September 2022 to September 2023. One hundred patients with acute appendicitis who underwent emergency appendectomy were included. Serum bilirubin (total and direct) levels were measured, and intraoperative findings were confirmed via histopathology. Statistical analysis was performed to determine the sensitivity, specificity, and predictive values of hyperbilirubinemia. Results: Mean total bilirubin levels were significantly higher in patients with complicated appendicitis (2.4 ± 0.9 mg/dL) compared to those with uncomplicated appendicitis (0.8 ± 0.3 mg/dL, p < 0.001). Direct bilirubin levels were also elevated (0.8 ± 0.4 mg/dL vs. 0.2 ± 0.1 mg/dL, p < 0.001). Hyperbilirubinemia showed a sensitivity of 88%, specificity of 65%, positive predictive value of 60%, and negative predictive value of 90% in predicting complicated appendicitis. Conclusion:Hyperbilirubinemia is a useful adjunctive marker for predicting complicated appendicitis, showing high sensitivity and a strong negative predictive value. Its integration into diagnostic protocols may aid in the timely identification and treatment of high-risk cases.