Background: There is a great deal of studies on the relationship between the existence of Helicobacter pylori (H. pylori) in oral cavity (dental plaque) and in stomach of patients, with conflicting results worldwide. The purpose of this study was to systematically review the existing litreature to assess if the dental plaque could be a source of gastric H. pylori infection and to explore the source of heterogeneity around it. Methods: We searched all the papers published since 2000 on international (Medline, ISI, Embase) databases using standard keywords. Two researchers evaluated the articles with standard critical appraisal form independently and those articles with the quality acquired greater than 70% were included in the study. The combined results were calculated with weighted average and the source of hetrogeneity was tested by meta-regression (random) model. Results: Finally, 23 studies were included (1861 patients). The prevalence of co-infection of gastric and dental plaque H. pylori was 49.7% (95% CI 16–83.4%) and the percent of agreement between the dental plaque H. pylori status and the gastric H. pylori was estimated as 82%. Only one study has reported that dental treatment has a preventive effect on the recurrence of gastric H. pylori infection. Conclusion: Co-infection of gastric H. pylori and dental plaque is reported by half of the studies. However, there is not enough evidence for the efficacy of dental treatment on prevention of recurrent gastric H. pylori infection.