Introduction Carriers of oncohematological diseases are at high risk for hepatitis B virus (HBV) infection. Objective and method To investigate the epidemiology of HBV infection in Goiânia, Central Brazil, 322 individuals with oncohematological diseases (leukemias, Hodgkin lymphoma and non-Hodgkin lymphoma) were interviewed and blood samples were collected for the detection of serological markers of HBV-DNA by polymerase chain reaction (PCR). Medical records of participants were also reviewed. Results Non-Hodgkin’s lymphomas ( n = 99) and chronic myeloid leukemia ( n = 108) were the most frequent oncohematological diseases. The overall prevalence of HBV was 13.97% (45/322). Of the total participants, 8.69% (28/322) presented isolated positivity for anti-HBs, suggesting low vaccine coverage. HBV-DNA was detected in 25% (1/4) of HBsAg positive samples and in 25% (3/12) of anti-HBc isolated, suggesting HBV occult infection. All samples were identified as subgenotype A1. Entries in patient records and the findings of this investigation suggest anti-HBc seroconversion during oncologic treatment. Age 50 years or over and use of a central catheter during therapy were associated with HBV exposure. Conclusion The low frequency of hepatitis B immunized individuals, detection of HBV DNA in HBsAg negative samples, and the suggestion of HBV exposure during treatment evidenced the potential for health-related viral dissemination in people with oncohematological diseases in our region, reinforcing the importance of serological monitoring, vaccination against hepatitis B, and adoption of strict infection control measures in these individuals.