Background: Helicobacter pylori infection remains an important global health problem and is particularly prevalent in Africa. However, estimates of infection prevalence vary substantially according to the diagnostic method used. Serological testing detects antibodies generated by exposure to H. pylori but may not reliably distinguish current from previous infection, whereas stool antigen testing provides evidence of current infection. This distinction is particularly important in high-prevalence settings where serological positivity may substantially exceed active-infection positivity. This study is aimed at comparing the prevalence and concordance of H. pylori serum antibody positivity, stool antigen positivity and faecal occult blood positivity among adults in Nigeria, and to examine the implications of discordant test results for interpretation and management of H. pylori infection. Methods: A cross-sectional study was conducted among 223 adults. Each participant was tested for H. pylori serum antibody, stool H. pylori antigen and faecal occult blood. The prevalence of positivity for each marker was determined. Associations between categorical test results were assessed using the chi-square test, with statistical significance set at p<0.05. Results: Serum H. pylori antibody positivity was substantially higher than stool antigen positivity, occurring in 169/223 participants (75.8%) compared with 23/223 (10.3%), respectively. Faecal occult blood was positive in 53/223 participants (23.8%). All participants with positive stool antigen results were also antibody-positive, demonstrating complete overlap between stool antigen positivity and seropositivity in this study. Antibody positivity was significantly associated with stool antigen positivity (χ²=6.789, p=0.009). Similarly, antibody positivity was significantly associated with faecal occult blood positivity (χ²=20.517, p<0.001). Stool antigen positivity was strongly associated with faecal occult blood positivity (χ²=32.574, p<0.001), with 17 of the 23-stool antigen-positive participants (73.9%) also having occult blood in stool. Conclusions: The study demonstrates a marked disparity between H. pylori seropositivity and stool antigen positivity in this Nigerian population. The substantially higher seroprevalence should not be interpreted as equivalent to current active infection. The findings support careful selection and interpretation of H. pylori diagnostic methods in high-prevalence settings and reinforce the importance of active-infection tests when the clinical objective is to identify current infection. The observed association between stool antigen positivity and faecal occult blood also warrants further investigation into the relationship between active H. pylori infection and gastrointestinal mucosal bleeding. Keywords: Helicobacter pylori; seroprevalence; stool antigen; active infection; faecal occult blood; diagnostic testing; Nigeria; concordance.