The most prevalent illnesses that affect the liver are viral infections; when the liver cell is destroyed by viruses, it loses its function and most of the body's processes are compromised. The liver is the primary source of serum cholinesterase. Therefore, serum cholinesterase can be used as a predictive biomarker for the liver's synthetic capability. This study aims to evaluate serum cholinesterase as a biomarker in patients with hepatitis B virus (HBV) or hepatitis C virus (HCV). The study was conducted at the Gastroenterology and Hepatology Teaching Hospital and Poisoning Consultation Center in Baghdad during the interval from November 2021 to March 2022. The liver function tests and serum cholinesterase were measured in one hundred fifty samples. Fifty patients with HBV and fifty patients with HCV were compared with fifty healthy individuals as a control group. The mean serum cholinesterase in the HBV and HCV patient groups (8528.76±2000.45 U/L and 7494.12± 2586.30 U/L, respectively) was lower than in the control group (9380.12±1848.96 U/L), and the difference was statistically significant (P < 0.05). The mean serum cholinesterase in the HCV patient group (7494.12±2586.30 U/L) was significantly lower (P < 0.05) than in the HBV patient group (8528.76 ±2000.45 U/L).