Abstract Hepatitis B virus reactivation (HBV-R) is a serious concern during cancer chemotherapy in patients with resolved HBV infection. We examined the levels of HBV surface (HBsAb) and core antibodies (HBcAb) to assess the incidence of HBV-R in patients with solid and hematopoietic cancers. Retrospective cohort study was conducted in 590 patients with resolved HBV infection. The patients consisted of solid (n = 466) and hematopoietic cancers (n = 124), including lymphoma receiving rituximab-containing chemotherapy. The incidenceof HBV-R was evaluated 761.5 (range, 4–3,898) days after the start of chemotherapy. Of 590 patients, 13 (2.2%) developed HBV-R after the start of chemotherapy. All HBV-R patients exhibited a lower HBsAb (<100 mIU/mL) at baseline. A higher HBcAb (≥100 C.O.I.) was identified as a risk factor for HBV-R,with an incidence of 9.6%. The simultaneous presence of HBsAb <100 mIU/mL and HBcAb ≥100 C.O.I. increased the risk of HBV-R by 18.5%. Patients treated with rituximab-containing chemotherapy had a higher risk of HBV-R (18.4%) despite having HBcAb <100 C.O.I. Our results indicate that baseline levels of HBsAb <100 mIU/mL and HBcAb ≥100 C.O.I are risk factors for HBV-R, except for the patients receiving chemotherapy containing rituximab.