The aim of this study was to detect the presence of Helicobacter pylori and Helicobacter heilmannii type II in dogs and evaluate the role of Helicobacter spp. in chronic gastritis. Gastroscopy was performed in a total of 40 dogs (22 symptomatic and 18 asymptomatic) admitted to the small animal clinic of Istanbul University. In this study, the density of spiral bacteria and the degree and type of gastritis by histopathology were determined. Rapid urease tests were performed on gastric biopsy samples, and the species identity was determined using nested polymerase chain reaction to assess for the presence of H. heilmannii type II and H. pylori. The relationship between symptoms and gastroscopic findings was significant (P < 0.001). Gastritis was diagnosed in 38 of the 40 dogs histopathologically, of which 71% were atrophic. Thirty-four dogs were found to be positive for H. heilmannii type II. Although general opinion indicates that dogs do not harbor H. pylori, 3 dogs with gastric symptoms and 1 asymptomatic dog were found positive for H. pylori in this study. No significant correlation was found between Helicobacter spp. density and gastritis severity. However, H. pylori had a high pathogenic effect as higher infiltration rates and increased intensity of mononuclear inflammatory cells and lymphoid follicles were observed in cases of H. pylori-related gastritis.