Background: As regard to high prevalence of Helicobacter pylori infection and complication of it, s persistence, as well as anti-bacterial activity against of it and anti-inflammatory properties of n-3 FAs, the present study was done with purpose of the effects of supplementation with EPA on the eradication of H.pylori, level of some serum inflammatory markers and total antioxidant capacity.Methods: Inadouble-blind, placebo-controlled clinical trial, 64 H. pyloripositive patients (31 patients in intervention group and 33 patients in control group), along with tetra-drugs H.pylori eradication regimen, randomly received daily 2 grams EPA supplement or MCT oil as placebo for 12weeks. Dietary intake data was collected by 24hour food recall and analyzed by Nutritionist IV software. Fasting blood, weight, height and level of physical activity were sampled and measured at the first and the end of the study.Results: Distribution of sex and mean of age, weight, daily intake of energy, macronutrients, micronutrients related to antioxidant status, level of physical activity and biochemical variables, didn, t have any differences between 2groups at the first of the study. Furthermore, significant differences in weight, level of physical activity and daily food intake was not seen in any of 2 groups before and after study. Eradication rate of infection, the level of interleukin-6 (IL-6), interleukin-8 (IL-8) and total antioxidant capacity (TAC) didnot have significant difference between 2 groups. The level of high sensitivity C-reactive protein (hs-CRP) statistically was decreased in EPA group (p=0.02).Conclusions: 12 weeks supplementation with EPA didnot have significant effect on eradication of H.pylori, serum level of IL-6, IL-8 and TAC, while it can decreases the level of hs-CRP.