Background: Liver histology remains the gold standard for assessing nonalcoholic fatty liver disease (NAFLD). Noninvasive serological markers have been developed to evaluate steatosis to avoid biopsy. In NAFLD patients, serum resistin was higher than those in control lean and obese patients. Objective of the study: To investigate serum resistin and its receptor gene expression in liver biopsy as predictors for NAFLD severity. Patients and methods: This study was conducted on 54 obese patients, with suspected fatty liver by ultrasound (excluding diabetic, alcoholic, hepatitis C virus antibody (HCVAb) or hepatitis B surface antigen (HBsAg) positive patients). They were subjected to anthropometric measurements, laboratory studies including serum resistin, abdominal ultrasonography (US) and liver biopsy. The 15 lean subjects were included as a control group. According to biopsy results, patients were subdivided into nonalcoholic steatohepatitis (NASH) group (46 patients) and non-NASH group (8 patients). Results: Significantly higher levels of resistin were detected in NAFLD patients compared to control subjects (p = 0.0001). Also, higher levels of resistin were recorded in NASH group compared to the non-NASH group; however, the difference was not statistically significant (p = 0.584). Serum alanine aspirate aminotransferase (AST), alanine aminotransferase (ALT) and gamma-glutamyl transpeptidase (GGT) were higher in NASH patients than non-NASH group (p = 0.223, p = 0.005 and p = 0.006 respectively). Abdominal US showed high sensitivity in NAFLD diagnosis (sensitivity of sonar in detecting steatosis grade compared to biopsy was 61% in grade 1, 25% in grade 2 and 75% in grade 3). Conclusion: Serum resistin can be combined with other noninvasive markers to predict the presence of NASH as an alternative to liver biopsy.