Helicobacter pylori colonizes the stomach and causes chronic gastritis, which most often remains asymptomatic. However, in a small proportion of infected persons, it causes peptic ulcers and gastric cancer. We reviewed recent evidence of the association between H. pylori infection and diabetes mellitus DM . Numerous studies have shown a positive association between H. pylori infection and DM, however, findings are still conflicting. Such a link is biologically plausible, given the importance of the stomach in the homeostasis of systems outside the digestive tract however, the mechanisms by which H. pylori might affect the risk of DM are not clear. Current knowledge indicates that H. pylori infection can affect the regulation of ghrelin and leptin, two hormones that play central roles in energy homeostasis in humans. Yet, methodological limitations are present in studies that addressed the relationships of H. pylori infection with DM and with possible risk factors for DM, including inadequate control of confounders. The important question of whether H. pylori eradication might be beneficial for glycemic control in diabetic patients is still unresolved. Future well-designed studies are needed to address these research questions, which are of clinical and great public health significance.