Inappropriate use of antibiotics during the COVID-19 pandemic has the potential to increase the burden of antimicrobial resistance. In this study, we report on the prevalence of antibiotic use and its associated factors among suspected and confirmed COVID-19 patients admitted to 35 health facilities in Sierra Leone from March 2020–March 2021. This was a cross-sectional study using routinely collected patient data. Of 700 confirmed COVID-19 patients, 47% received antibiotics. The majority (73%) of the antibiotics belonged to the ’WATCH’ group of antibiotics, which are highly toxic and prone to resistance. The most frequently prescribed antibiotics were azithromycin, ceftriaxone, amoxicillin, metronidazole, and amoxicillin-clavulanic acid. Antibiotic use was significantly higher in patients aged 25–34 years than in those with severe disease. Of 755 suspected COVID-19 patients, 61% received antibiotics, of which the majority (58%) belonged to the ‘WATCH’ category. The most frequently prescribed antibiotics were ceftriaxone, metronidazole, azithromycin, ciprofloxacin, and amoxycillin. The prevalence of antibiotic use among suspected and confirmed COVID-19 patients admitted to healthcare facilities in Sierra Leone was high and not in line with national and WHO case management guidelines. Training of health care providers, strengthening of antimicrobial stewardship programs, and microbiological laboratory capacity are urgently needed.