Background – Since cancer is a common and often serious disease, the potential impact of the health crisis linked to the COVID-19 pandemic on cancer incidence (i.e., on the number of newly diagnosed cancers) is a major public health concern. The objective of this study was to conduct an initial indirect estimate of this impact in France based on temporal variations in the number of patients hospitalized for a new cancer. Materials and Methods – Hospital data from 2010 to 2021 were extracted from the National Health Data System. First, a graphical description of the monthly number of patients hospitalized for a new cancer (as the primary diagnosis) before and during the pandemic was produced (from 2018 to 2021). Next, to measure the impact of the health crisis more directly, we compared the observed annual numbers of patients hospitalized for a new cancer in 2020 and 2021 with expected numbers estimated by projecting the modeled trends from 2010 to 2019. Results – The graphical representation showed a clear shortfall in the number of patients hospitalized for a new cancer at the time of the first lockdown (March to May 2020). Based on modeling and projections, the annual deviation from expected numbers was estimated to be -5% (95% confidence interval, 95% CI: [-7.0; -2.9]) in 2020 and -0.9% [-3.5; 1.9] in 2021. Cancers eligible for organized screening or for which surgery could be postponed were more affected than cancers with a poor prognosis, such as liver or pancreatic cancers. The shortfall in the number of patients hospitalized for a new cancer in 2020 was observed in all regions of France, as well as in the overseas departments and regions. Discussion – The impact of the health crisis caused by the COVID-19 pandemic on the number of patients hospitalized for a new cancer in France was evident during the first lockdown in 2020, and the shortfall does not appear to have been offset in 2021 (no excess observed). Furthermore, the indicators studied only partially reflect delays in diagnosis and their many potential consequences. The assessment of the pandemic’s impact in all its dimensions must be continued and refined, particularly using observed incidence data from cancer registries, which will be available in 2023 for diagnoses made in 2020.