To characterize predictors of isolated hepatitis B core antibody (anti-HBc) among human immunodeficiency virus (HIV)-infected and HIV-uninfected women, we compared 702 women with anti-HBc and hepatitis B surface antibody (anti-HBs) with 490 women with isolated anti-HBc (1.8% of whom had detectable hepatitis B virus [HBV] DNA). Factors independently associated with isolated anti-HBc without viremia were detectable hepatitis C virus (HCV) RNA, HIV positivity, history of injection drug use, >10 lifetime sex partners, and HIV RNA level >100,000 copies/mL. Anti-HBs levels were lower among anti-HCV-positive women. Isolated anti-HBc was rarely explained by occult HBV in this cohort but may be explained by the influence of viral coinfections on anti-HBs level or durability.