Background and Objective: Hepatitis B virus is one of the hepadnaviruses which is an important cause of acute and chronic hepatitis, cirrhosis and hepatocellular carcinoma. Currently, prenatal transmission is the most important spreading route of hepatitis B in Iran and probability of its conversion into asymptomatic carrier in newborns of these women is high. Thus, this study was designed in order to have more accurate information about its prevalence among pregnant women in Zanjan city. Materials and Methods: In this cross-sectional descriptive study, from 1317 pregnant women who referred to healthcare centers, 2 mL blood sample was taken and after centrifugation the serums were kept frozen in -20℃. ELISA kit was used for measuring HBs-Ab and Immuno affinity chromatography was used for HBs-Ag measurement. Results: In this study, the prevalence of HBs-Ag and HBs-Ab was 0.4% and 38.4%, respectively. There was no correlation among the HBs-Ag positive individuals, history of jaundice, different age groups, and location. However, a statistically significant relationship was found between education level and positive HBs-Ag, as well as the history of vaccination against hepatitis B and the positive HBs-Ab. Conclusion: According to the results, it seems that parrallel to increase in education and awareness level, especially in pregnant women, the incidence and consequences of the chronic form of this disease has been reduced.