The few published studies on the relationship between Helicobacter pylori infection and metabolic homeostasis were relatively small and yielded inconsistent results. We examined the prevalence of metabolic syndrome in relation to H. pylori infection and its symptoms in a large and unselected population. Coded data from the computerised database of a large health maintenance organisation in Israel were accessed for 147,936 individuals 25-95 years of age who performed the urea breath test during 2002-2012. The classification of metabolic syndrome followed a modified definition of the international diabetes federation. Prevalences of H. pylori infection and metabolic syndrome were 52.0% and 11.4% respectively. H. pylori infected patients had increased likelihood of metabolic syndrome: adjusted odds ratio (aOR) 1.15 (95% confidence intervals (CI) 1.10-1.19), as did patients with gastric ulcer: aOR 1.15 (95% CI 1.03-1.28) vs patients without these conditions. Duodenal ulcer was associated with metabolic syndrome only in persons aged 25-34 years: aOR 1.59 (95% CI 1.19-2.13), but not in older persons (P = 0.001 for heterogeneity). In conclusion, the likelihood of metabolic syndrome appeared significantly increased in relation to H. pylori infection and gastric and duodenal ulcers. These findings suggest that H. pylori long-term gastric inflammation might play a role in metabolic homeostasis.