Background: There have been few reports on secondary bacteremia in patients hospitalized with COVID-19. We aimed to analyze the onset time of secondary bacteremia after the onset of illness and hospital admission and determine the proportion of secondary bacteremia on blood cultures drawn from patients with COVID-19. Methods: We conducted a retrospective cohort study of all hospitalized patients with COVID-19 who took blood culture tests between January 1, 2020 and September 30, 2021 at Kyoto City Hospital, Japan. Results: Of 507 patients hospitalized with COVID-19, blood culture tests were performed in 169. Eleven of them had secondary bacteremia, and 158 had a negative blood culture test. The onset time with the highest proportion of secondary bacteremia in blood cultures drawn from the day of symptom onset and hospitalization was from 11th-15th day (12.8%) and 6th-10th day (18.2%), respectively. The median time in which patients were diagnosed with secondary bacteremia from the onset of COVID-19 symptoms and hospital admission was 12.5 [interquartile range (IQR) 12-19.5] days and 6 (IQR 5-9) days, respectively. Conclusions: The timing from symptom onset and hospital admission may be a valuable indicator for making a clinical decision of taking blood cultures in patients hospitalized with COVID-19.