ABSTRACT BACKGROUND: The clinical course of gastric lymphoma is heterogeneous and clinical symptoms and some factors have been related to prognosis. OBJECTIVE: The present study aims to identify prognostic factors in gastric diffuse B-cell non-Hodgkin lymphoma diagnosed and treated in different countries. METHODS: A consecutive series of gastric diffuse B-cell non-Hodgkin lymphoma patients diagnosed and treated in Brazil, Portugal and Italy, between February 2008 and December 2014 was evaluated. RESULTS: Of 104 patients, 57 were female and the median age was 69 years (range: 28-88). The distribution of the age-adjusted international prognostic index was 12/95 (13%) high risk, 20/95 (21%) high-intermediate risk and 63/95 (66%) low/low-intermediate risk. Symptoms included abdominal pain (63/74), weight loss (57/73), dysphagia (37/72) and nausea/vomiting (37/72). Bulky disease was found in 24% of the cases, anemia in 33 of 76 patients and bleeding in 22 of 72 patients. The median follow-up time was 25 months (range: 1-77 months), with 1- and 5-year survival rates of 79% and 76%, respectively. The multivariate Cox Regression identified the age-adjusted international prognostic index as a predictor of death (hazard risk: 3.62; 95% confidence interval: 2.21-5.93; p-value <0.0001). CONCLUSIONS: This series identified the age-adjusted international prognostic index as predictive of mortality in patients treated with conventional immunochemotherapy.