Human hepatitis B virus (HBV) infection remains a serious public health problem worldwide, as it is one of the main risk factors for hepatocellular carcinoma (HCC). Cross-species transmission of HBV has been reported in non-human primates, and pigs may also be infected with HBV or an HBV-like agent. The purpose of this study was to demonstrate the presence of HBV antigens and anti-HBV antibodies in pig sera, providing further support for the existence of HBV or an HBV-like agent in pig populations. The HBV surface antigen (HBsAg) and HBV e antigen (HBeAg) in pig serum samples were detected using HBsAg and HBeAg ELISA Kits, respectively. Antibodies to HBsAg and the Hepatitis B core antigen (HBcAg) in serum samples were also detected using anti-HBsAg and anti-HBcAg antibody ELISA Kits, respectively. HBsAg and HBeAg were detected in 7 of 442 (1.6%) and 7 of 184 (3.8%) pig serum samples, respectively. Furthermore, antibodies specific to HBsAg and HBcAg were identified in 45 of 442 (10.2%) and 39 of 434 (9.0%) pig serum samples, respectively. However, neither HBV DNA nor antibodies to HBeAg were detected in 409 and 298 pig serum samples, respectively. HBV antigens and anti-HBV antibodies were both present in a considerable number of pig serum samples, suggesting that pigs could be infected with a variant HBV or an HBV-like agent. Further studies will be necessary to confirm cross-species infection of pigs with HBV.