CD3 antigen represents the most specific as well the most sensitive T cells lineage marker, including NK and NKT. Aim and methods: our study was to evaluate CD-3 in nonalcoholic steatohepatitis patients as a diagnostic and prognostic marker in such patients. Serum samples were collected from 41 NAFLD patients, in addition to 14 healthy subjects. They were recruited from the internal medicine department - Cairo University. All patients and controls were subjected to clinical assessment, abdominal ultrasound examination, laboratory assessment including liver function and enzymes, kidney function, and lipid profile. Fib-4 and NAFLD fibrosis score were calculated for all patients. Also, serum levels of CD-3 were detected by ELISA technique. Results: The NAFLD patients group was divided into three groups: fifteen obese patients, fourteen diabetic patients, twelve obese patients with T2DM. BMI, HbA1C, and cholesterol levels were significantly elevated in the NAFLD cases compared with healthy controls (p<0.05). The mean serum level of CD3 was 64.53±84 ng/ml in NAFLD cases vs. 4.76±2.94 ng/ml in controls. Overall, there was a statistically significant increase in serum CD3 levels in NAFLD cases (p<0.001). Additionally, serum level of CD3 was significantly higher in the diabetic non-obese subjects and obese non-diabetic subjects when compared with the lean subjects (89.4±113.53 ng/ml and 60.91±73.76 vs. 4.76±2.94 ng/ml, P = 0. 003& 0.05; respectively. Conclusion: Serum level of CD3 can be used as a prognostic marker in cases with NAFLD as they increase with the progression of the disease and is correlated with fibrosis stage.