Introduction: To investigate the clinical characteristics and outcomes of cancer patients with COVID-19 infections and evaluate the effect of hepatitis B immunization status on susceptibility to COVID-19 infection and mortality risk. Materials and methods: The records of 1,515 patients who presented to the Medical Oncology clinic between March 2020 and December 2020 were analysed retrospectively. The demographic and clinical characteristics and laboratory findings of cancer patients with (case group) and without (control group) COVID-19 infection were compared. Results: Of the 1,515 patients, 153 (10.1%) had been diagnosed with COVID-19, and the median age of cancer patients with COVID-19 infection was 53.9 (range; 18–82) years. The most common types of cancer were breast cancer (26.2%), gastrointestinal system cancers (22.3%), genitourinary-system cancers (16.5%) and lung cancer (15.5%). The presence of metastatic disease [hazard ratio (HR): 0.09, 95% CI (0.01–0.83), (p = 0.03)] and receipt of palliative chemotherapy in the cancer patients with COVID-19 infections [HR: 0.1, 95% CI (0.01–0.69), (p = 0.02)] were identified as prognostic factors in multivariate analysis as univariate analysis did not indicate palliative treatment as a prognostic factor. When the case group and control groups were compared in terms of hepatitis B immunization status (p = 0.24), no statistically significant difference was identified between the two groups. Furthermore, hepatitis B immunization status (p = 0.37) were not found to be associated with COVID-19-related mortality risk. Conclusion: Hepatitis B immunization status were not associated with the risk of COVID-19 transmission and mortality. The present study identified the presence of metastatic disease and palliative chemotherapy as negative and positive prognostic factors, respectively.