IMPORTANCEMany insurers waived cost sharing for COVID-19 hospitalizations during 2020. Nonetheless, patients may have been billed if their plans did not implement waivers or if waivers did not capture all hospitalization-related care. Assessment of out-of-pocket spending for COVID-19 hospitalizations in 2020 may show the financial burden that patients may experience if insurers allow waivers to expire, as many chose to do during 2021. OBJECTIVE To estimate out-of-pocket spending for COVID-19 hospitalizations in the US in 2020. DESIGN, SETTING, AND PARTICIPANTS This cross-sectional study used data from the IQVIA PharMetrics Plus for Academics Database, a national claims database representing 7.7 million privately insured patients and 1.0 million Medicare Advantage patients, regarding COVID-19 hospitalizations for privately insured and Medicare Advantage patients from March to September 2020. MAIN OUTCOMES AND MEASURES Mean total out-of-pocket spending, defined as the sum of out-of-pocket spending for facility services billed by hospitals (eg, accommodation charges) and professional and ancillary services billed by clinicians and ancillary providers (eg, clinician inpatient evaluation and management, ambulance transport).RESULTS Analyses included 4075 hospitalizations; 2091 (51.3%) were for male patients, and the mean (SD) age of patients was 66.8 (14.8) years. Of these hospitalizations, 1377 (33.8%) were for privately insured patients. Out-of-pocket spending for facility services, professional and ancillary services, or both was reported for 981 of 1377 hospitalizations for privately insured patients (71.2%) and 1324 of 2968 hospitalizations for Medicare Advantage patients (49.