Determination of hepatitis B virus (HBV) infections in key populations including prison inmates is crucial for formulating appropriate intervention approaches. However, in many low-income countries, such as Liberia, there is hardly any documentation on HBV prevalence among inmates. This study determined and evaluated the prevalence of HBV infections among incarcerated persons in the Monrovia Central Prison, Liberia. One hundred participants comprising 76 males and 24 females were studied. Participants’ demographic and potential risk factors information were obtained using a semi-structured questionnaire, and blood samples were collected for the analysis. Plasma was tested for five HBV serological markers, namely, HBsAg, HBsAb, HBeAg, HBeAb, and HBcAb. The seroreactivity of actively infected persons was confirmed by nucleic acid detection. Results of the serological assay showed that 34% of the participants had been exposed to the virus and 14% were actively infected. qPCR confirmed HBV DNA in seven actively infected samples. Statistical analysis indicated that a low level of education, a history of blood transfusion, and intravenous drug use, were significant predictors of active HBV infection and HBV exposure, respectively. These findings might make the testing and vaccination of convicts against HBV infection prior to their admission into prison facilities imperative.