Background: Pro-inflammatory cytokines are associated with systemic inflammatory responses. Objective: To investigate the levels of pro-inflammatory cytokines (IL-1b, IL-6, and TNF-a) in patients with non-alcoholic fatty liver (NAFL) and non-alcoholic steatohepatitis (NASH) compared to healthy individuals. Methods: This case-control study was conducted on 30 patients with NAFL, 30 patients with NASH, and 30 healthy volunteers. The plasma level of IL-1b, IL-6, and TNF-a were determined by ELISA, and biochemical parameters were measured using colorimetric methods. Results: IL-1b and IL-6 levels were significantly higher in patients with NASH compared with NAFL and control group. However, TNF-a levels had no significant variations in NAFL and NASH patients compared to the control group (p=0.903 and p=0.960, respectively). Conclusion: Results showed that the levels of ALT activity and pro-inflammatory cytokines were higher in patients with NASH compared to control and NAFL subjects; Therefore, steatosis and inflammation develop as a result of excessive pro-inflammatory factors in NASH.