IMPORTANCEThe COVID-19 pandemic and the containment and mitigation measures taken were feared to be associated with increased child abuse. OBJECTIVE To investigate the trend of abusive head trauma (AHT) incidence and severity in infants during the COVID-19 pandemic. DESIGN, SETTING, AND PARTICIPANTSIn a time-series analysis of a longitudinal, populationbased, cohort study, all consecutive cases of AHT in infants younger than 12 months old referred between January 2017 and December 2021 to Necker Hospital for Sick Children, the single regional pediatric neurosurgery center for the Paris metropolitan area, were included. AHT was defined as 1 or more subdural hemorrhage and a positive multidisciplinary evaluation after a social, clinical, biological, and radiological workup. Data were analyzed from January to March 2022. MAIN OUTCOMES AND MEASURESThe primary outcome was the monthly incidence of AHT, which was analyzed using Poisson regression modeling. Secondary outcomes included mortality and severe morbidity and were studied with logistic and linear regressions. The monthly incidence of neurosurgical interventions for hydrocephalus was used as a control series. RESULTS Among the 99 included infants with AHT (median [IQR] age, 4 [3-6] months; 64 boys[65%]), 86 of 99 (87%) had bridging vein thrombosis, 74 of 99 (75%) had retinal hemorrhages, 23 of 72 (32%) had fractures, 26 of 99 (26%) had status epilepticus, 20 of 99 (20%) had skin injuries, 53 of 99 (54%) underwent neurosurgical interventions, and 13 of 99 (13%) died. Compared with the prepandemic period (2017-2019), AHT incidence was stable in 2020 (adjusted incidence rate ratio, 1.02; 95% CI, 0.59-1.77) and then significantly increased in 2021 (adjusted incidence rate ratio, 1.92; 95% CI, 1.23-2.99). The severity of AHT worsened in 2021 in terms of mortality (odds ratio 9.39; 95% CI, 1.88-47.00). Other secondary outcomes and the control series were not significantly modified. CONCLUSIONS AND RELEVANCEIn this cohort study, a marked increase in AHT incidence and severity occurred during the COVID-19 pandemic in the Paris metropolitan area. These results suggest the need for clinical awareness and preventive actions.