Introduction: The aim of this study was to determine the prevalence of exposure to hepatitis A by means of serologic markers in chronic hepatitis B patients, with the secondary aim of finding the best prevention method for hepatitis A infection in susceptible groups of our setting. Methods: During the period between 2016 and 2017, we recruited 403 hepatitis B patients aged more than 14 years and regularly attending the infectious diseases clinic at a referral university hospital, Tehran, Iran. A blood sample was collected from all the patients and tested for hepatitis A IgG. The data was analyzed by SPSS v.19. Results: Although none of the patients had previously received hepatitis A vaccine, the results for serologic level of hepatitis A IgG, demonstrated positive results in 379 (94%) cases. The mean age of patients with negative and positive IgG was 29.17 and 42.46 years, respectively; the difference was statistically significant (P≤0.001). The majority of seronegative patients were young adults aged < 25 years and 25 to 35 years (P <0.001). Conclusion: Seroprevalence of hepatitis A in chronic HBV patients in Iran is high. As HBV infected patients younger than 35 years could be seronagative for HAV infection, evaluation of these patients for HAV infection and vaccination of seronegative patients would be a reasonable approach.