Introduction: Hepatitis B core (anti-HBc) antibody is an effective marker for occult Hepatitis B virus (HBV) infection and is an integral part of blood donor screening in many countries. This study was aimed to evaluate the prevalence of anti-HBc antibodies among voluntary blood donors in Thailand and its significance to reduce the risk of transfusion transmitted HBV infection. Methods: A total of 3,197 voluntary blood donor samples that were pre-screened non-reactive for HBs-Ag serology and HBV ID-NAT were tested for anti-HBc Total and IgM antibody and anti-HBs titers on ARCHITECT i6000 (Abbott Diagnostics, Illinois) between May 1, 2017 and September 31, 2017 at the National Blood Centre,