Hepatitis B infection is the leading cause of chronic hepatitis, cirrhosis and hepatocellular carcinoma and is thought to be responsible for million deaths per year globally. Management of patients with resolved or active hepatitis B and cancer is a challenge and these patients are at higher risk of hepatitis B related complications due to immunosuppression and loss of prior immunity. The treating hematologist needs to understand the biology of this common virus, its potential for long-term harm, the necessary laboratory monitoring for their identification and characterization, and the pharmacological interventions for their control. This review offers a general approach to prevention and treatment of hepatitis B reactivation in patients with hematological malignancies and transplant recipients. Practitioners are also encouraged to seek advice and consultation from experts in the design of specific protocols for screening, monitoring and prevention..