Objective: The differences in clinical outcomes in hospitalized patients with hematological disorders (HD) who developed either coronavirus disease 2019 (COVID-19) or seasonal influenza (SI) are not fully understood. To examine these differences, we retrospectively analyzed the baseline characteristics and clinical outcomes of hospitalized patients with HD admitted from 2016 to 2021.Patients and Methods: Patients with HD who developed COVID-19 (in the past 1 year) (n=21) or SI (in the past 5 years) (n=23) in the Department of Hematology/Oncology, Asahikawa Kosei General Hospital were evaluated.Results: The median ages of the patients with HD with either COVID-19 or SI were 80 and 68 years, respectively (P=0.03). The groups showed no significant differences in sex ratio, body mass index, or Eastern Cooperative Oncology Group performance status. In the COVID-19 and SI groups, the most common primary diseases were diffuse large B-cell lymphoma (43%) and multiple myeloma (39%), respectively. The median numbers of days of oxygen administration (8 vs. 0 days), quarantine (25 vs. 6 days), and hospitalization (72 vs. 21 days) were significantly higher in HD patients with COVID-19 than those in HD patients with SI (all P<0.001). The overall 90-day survival of patients with HD and COVID-19 was significantly shorter than that of patients with HD and SI (P=0.019). Moreover, patients with HD and COVID-19 had a higher risk of in-hospital mortality (43% vs. 9%; odds ratio, 7.50; 95% confidence interval, 1.26–82.4; P=0.01) compared to patients with HD and SI.Conclusion: Patients with HD and COVID-19 required longer periods of in-hospital medical and showed poorer survival than those with SI. During the COVID-19 pandemic, hematologists should closely monitor the condition of patients with COVID-19 to closely monitor their condition to prevent deaths.