A two-arm randomized open labeled controlled clinical trial was conducted on 50 patients with non-alcoholic fatty liver disease (NAFLD). Participants were assigned to take either a lifestyle modification (LM), or LM +30 g/day brown milled flaxseed for 12 weeks. At the end of the study, body weight, liver enzymes, insulin resistance and hepatic fibrosis and steatosis decreased significantly in both groups (p 0.05); however, this reduction was significantly greater in those who took flaxseed supplementation (p 0.05). The significant mean differences were reached in hepatic markers between flaxseed and control group, respectively: ALT [-11.12 compared with -3.7 U/L; P 0.001], AST [-8.29 compared with -4 U/L; p 0.001], GGT [-15.7 compared with -2.62 U/L; p 0.001], fibrosis score [-1.26 compared with -0.77 kPa; p = 0.013] and steatosis score [-47 compared with -15.45 dB/m; p = 0.022]. In conclusion, flaxseed supplementation plus lifestyle modification is more effective than lifestyle modification alone for NAFLD management.