BACKGROUND: The fear of contracting COVID-19 and the preventive measures taken during the health crisis impacted both people's lifestyles and the health system. This nationwide study aimed to investigate the impact of the first wave of the COVID-19 pandemic on hospitalizations and mortality related to geriatric syndromes (GS) in older adults in France. METHODS: The French National Health Data System was used to compare hospital admissions (excluding main diagnosis of COVID-19) and mortality rates (using multiple-cause and initial-cause analyses, and both including or excluding confirmed/probable COVID-19) related to 10 different GS (dementia, other cognitive disorders and symptoms, delirium/disorientation, depression, undernutrition/malnutrition, dehydration, pressure ulcer, incontinence, fall/injury and femoral neck fracture) from January to September 2020 to rates observed in previous years. Analyses were stratified by age, sex, place of residence or place of death, and region. RESULTS: Hospitalization rates for all GS decreased during the first lockdown compared to the same periods in 2017-2019 (from -59% for incontinence to -13% for femoral neck fractures). A dose-response relationship was observed between reduced hospitalizations and COVID-19-related mortality rates. Conversely, for almost all GS studied, excess mortality without COVID-19 was observed during this lockdown compared to 2015-2017 (from +74% for delirium/disorientation to +8% for fall/injury), especially in nursing homes and at home. CONCLUSIONS: In France, during the first lockdown, a substantial decrease in hospitalizations for GS was accompanied by excess mortality. This decline in use of services, which persisted beyond lockdown, may have a mid- and long-term impact on older adult's health.