-Background -Helicobacter pylori (H. pylori) gastric infection is a main cause of inflammatory changes and gastric cancers. Objective -The aim of this study was finding the effects of curcumin on oxidative stress and histological changes in chronic gastritis associated with H. pylori. Me thods -In a randomized clinical trial, patients were divided into two groups: a standard triple therapy group and triple therapy with curcumin group. Endoscopic and histological examinations were measured for all patients before and after 8 weeks. Results -Triple therapy with curcumin treatment group significantly decreased malondialdehyde markers, glutathione peroxides and increased total antioxidant capacity of the gastric mucosa at the end of study compared to baseline and triple regimen groups. In addition, the oxidative damage to DNA was significantly decreased in triple therapy with curcumin group at the end of study compared to baseline and compared to triple therapy (P<0.05 for both). Triple therapy group in combination with Curcumin significantly decreased all active, chronic and endoscopic inflammation scores of patients compared to the baseline and triple therapy group (P<0.05 for both). The eradication rate by triple therapy + curcumin was significantly increased compared to triple therapy alone (P<0.05). Conclusion -Curcumin can be a useful supplement to improve chronic inflammation and prevention of carcinogenic changes in patients with chronic gastritis associated by H. pylori. HEADINGS -Gastritis. Helicobacter pylori. Curcumin. Oxidative stress. DNA damage.Declared conflict of interest of all authors: none Disclosure of funding: no funding received