Background: COVID-19 pandemic has ignited the urge for repurposing old drugs as candidate antiviral medicines to treat novel challenges of viral infections. Niclosamide (NCS) is an anti-parasitic drug of known antiviral potential. Therefore, this study attempts to investigate the antiviral effect and safety of NCS on SARS-CoV-2 caused COVID-19 patients. Methods: Randomized controlled open label clinical trial encompassed 75 COVID-19 patients treated with standard of care plus NCS were included as experimental group and 75 COVID-19 patients treated with only standard of care therapy as control group. Each group was composed of 25 mild, 25 moderate and 25 severe patients. Survival rate, time to recovery, and side effects were the main endpoints for the assessment of the therapeutic effect and safety of NCS. Results: NCS did not enhance survival rate as three of severe COVID-19 patients in NCS and in control groups died (P>0.05). However, NCS, compared to control group, reduced the time to recovery in moderate and severe COVID-19 patients about 5 and 3 days, respectively but not in mild patients (P≤0.05). Most interestingly, NCS lowered time to recovery up to five days in patients with co-morbidities (P≤0.05) whereas only one day lowered in patients without co-morbidities (P>0.05). Conclusion: It is concluded that NCS accelerates time to recovery about 3 to 5 days in moderate to severe COVID-19 patients especially those with co-morbidities; hence, NCS is of clinical benefit for freeing hospital beds for more patients in pandemic crisis.