Background: The COVID-19 pandemic lead to a massive shutdown of social life in Germany starting in March 2020. Elective medical treatment was substantially reduced but urgent diagnostics and treatment including cancer care should not have been affected.Materials And Methods: We analyzed the number of oncology admissions to 75 German Helios hospitals during 2 time periods in 2020 and compared the data with the respective periods in 2019. The study included nearly 69,000 admissions in total.Results: A highly significant reduction in overall cancer admissions was seen for the early lockdown period from 13 March to 28 April 2020 compared to the same period in 2019. After an official communication advising the health system to return to normal practice on 29 April 2020, we again found a highly significant difference in admissions compared to the respective time in the previous year. Subgroup analysis shows a significant impact of age >75 years, high hospital volume, and intermediate or high COVID-19 case volume in the federal states. Gender had no impact on admission numbers. The effects and significance levels were comparable in nearly all different diagnostic subgroups according to the ICD codes.Conclusions: For cancer diagnosis and treatment, we found a statistically significant decrease in hospital admissions in the range of 10-20% for both study periods in comparison to the previous year.