Helicobacter pylori (H. pylori) is widely known as a cause of gastric disorders. Presence of H. pylori in dental pulp has been reported. Dental caries may influence the presence or absence of systemic H. pylori infection by serving as a source of H. pylori. In this cross-sectional study, we examined whether H. pylori infection in blood were associated with dental caries in Japanese adults. The participants were 752 individuals (513 males and 239 females, mean age 53.8 years) who underwent both H. pylori testing (H. pylori antibody test and pepsinogen test) and dental checkups at the Asahi University Hospital Human Health Center between April 2018 and March 2019. Those diagnosed as positive for H. pylori antibody test or positive for serum pepsinogen test as H. pylori test in the human health checkup were judged as those with H. pylori infection in the blood. In our study, 83 participants (11%) were determined to be infected with H. pylori in the blood. The proportion of those with decayed teeth was higher in participants with H. pylori infection in blood than in those without H. pylori infection in blood (p< 0.001). The logistic analysis showed that presence of H. pylori infection in blood was positively associated with those with decayed teeth (OR, 5.656; 95% CI, 3.374 to 9.479) after adjusting for age, gender, gastric disease, regular dental checkups, antibiotic medication history, and decayed teeth. Furthermore, the proportion of H. pylori infection in blood increased according to number of decayed teeth (p< 0.001). The results indicate that H. pylori infection in blood were associated with decayed teeth. Untreated dental caries may have an impact on systemic H. pylori infection.