Helicobacter pylori (H. pylori) is one of the most common chronic infections in patients with gastrointestinal disorders. Recent reports suggested that H. pylori might have high prevalence among patients with diabetes. The aim of this cross-sectional study was to assess the prevalence of H. pylori infection in diabetes mellitus and to study the relationship between histological findings and H. pylori infection in diabetic patients. Eighty patients with dyspepsia that were referred to our gastrointestinal department between May 2007 and May 2008 were included in our study. We checked fasting blood sugar for all of the study samples. All of patients underwent upper endoscopy and biopsy specimens were obtained from the antrum and the corpus. The specimens for the presence of H. pylori were colored by Giemsa stains. A single pathologist evaluated the histology slides. We found that prevalence of H. pylori infection was significantly higher in diabetics than in non-diabetics (P=0.001). Indeed, the prevalence of gastritis did differ significantly between the two groups (P=0.001). According to our results diabetes mellitus is one of the risk factor that must be considered in evaluation of H. pylori infection in diabetic patients with dyspepsia.