Aim:To determine the correlation of Helicobacter pylori infection with peripheral blood neutrophil/lymphocyte ratio (NLR) and mean platelet volume (MPV).Materials and methods:The NLR, MPV, platelets, leukocytes, neutrophils, and lymphocytes were calculated and the differences between groups were investigated.Results:A total of 199 patients were included in the study. Neutrophil/lymphocyte ratio was statistically lower in H. pylori-positive patients than in H. pylori-negative patients (1.94 ± 0.79 vs 2.67 ± 2.35 respectively, p = 0.04). There was no significant difference between H. pylori-negative patients and H. pylori-positive patients of severe intensity in terms of MPV. However, peripheral blood lymphocytes and platelets were statistically significantly higher in H. pylori-positive patients of severe intensity (lymphocytes 2150 ± 826 vs 2954 ± 2436 respectively, p = 0.000 and platelets 258247 ± 69494 vs 265611 ± 113397 respectively, p = 0.02) compared with H. pylori-negative patients.Conclusion:A moderate increase in the intensity of H. pylori does not lead to a significant change in MPV as measured by hemogram; however, it gives rise to a statistically significant fall in NLR. Presence of severe H. pylori-positive intensity leads to a statistically significant increase in peripheral blood lymphocytes and platelets compared with H. pylori-negative patients.How to cite this article: Guclu M, Agan AF. Association of Severity of Helicobacter pylori Infection with Peripheral Blood Neutrophil to Lymphocyte Ratio and Mean Platelet Volume. Euroasian J Hepato-Gastroenterol 2017;7(1):11-16.