Hepatitis B virus infection poses a significant public health challenge among pregnant women in sub-Saharan Africa, including Ethiopia, where it is often underdiagnosed and underreported. This study aimed to determine the seroprevalence and associated factors of hepatitis B virus infection among pregnant women attending antenatal care in public hospitals in the Central Ethiopian region. A hospital-based cross-sectional study was conducted from October 1, 2023, to March 1, 2024, among 482 pregnant women selected using systematic random sampling. Blood samples were collected and tested for hepatitis B surface antigen, and data were gathered using a structured, interviewer-administered questionnaire. Data were entered into Epi Data version 3.1 and analyzed using SPSS version 26. Logistic regression analysis identified factors associated with hepatitis B infection, with significance at p < 0.05. The response rate was 98.8%. Most participants (66.2%) were aged 18-28 years, with a mean age of 28. The overall seroprevalence of hepatitis B virus infection was 12.8% (95% CI: 10.1, 16.2). A maternal educational level of diploma and above (AOR: 0.23; 95% CI: 0.09, 0.62) and no history of hospital admission (AOR: 0.23; 95% CI: 0.10, 0.53) were linked to a lower risk. In contrast, being unable to read and write (AOR: 2.67; 95% CI: 1.14, 6.26), having a medium (4-6) or large (≥7) family size (AOR: 2.34; 95% CI: 1.15, 4.78) and (AOR: 3.65; 95% CI: 1.33, 10.04), respectively, history of traditional delivery care (AOR: 2.46; 95% CI: 1.04, 5.84), and history of abortion (AOR: 2.90; 95% CI: 1.37, 6.11) were associated with higher risk. Hepatitis B virus infection remains highly prevalent among pregnant women in the study area. Strengthening family-centered healthcare, improving screening and vaccination coverage, and enhancing community-based awareness and prevention initiatives are essential to reduce the burden of infection.