Background High rates of antibiotic use (AU) among inpatients with coronavirus disease 2019 (COVID-19) despite low rates of bacterial coinfection and secondary infection have been reported. We evaluated the impact of the COVID-19 pandemic on AU in healthcare facilities (HCFs) in South America. Methods We conducted an ecologic evaluation of AU in inpatient adult acute care wards in 2 HCFs each in Argentina, Brazil, and Chile. The AU rates for intravenous antibiotics were calculated as the defined daily dose per 1000 patient-days, using pharmacy dispensing records and hospitalization data from March 2018-February 2020 (prepandemic) and March 2020-February 2021 (pandemic). Differences in median AU were compared between the prepandemic and pandemic periods, using the Wilcoxon rank sum test to determine significance. Interrupted time series analysis was used to analyze changes in AU during the COVID-19 pandemic. Results Compared with the prepandemic period, the median difference in AU rates for all antibiotics combined increased in 4 of 6 HCFs (percentage change, 6.7%-35.1%; P < .05). In the interrupted time series models, 5 of 6 HCFs had significant increases in use of all antibiotics combined immediately at the onset of the pandemic (immediate effect estimate range, 15.4-268), but only 1 of these 5 HCFs experienced a sustained increase over time (change in slope, +8.13; P < .01). The effect of the pandemic onset varied by antibiotic group and HCF. Conclusions Substantial increases in AU were observed at the beginning of the COVID-19 pandemic, suggesting the need to maintain or strengthen antibiotic stewardship activities as part of pandemic or emergency HCF responses.