Inosine pranobex (IP), an immunomodulatory agent, is used in the treatment of various viral infections. The results of a phase 3 randomized controlled trial are reported, evaluating the efficacy and safety of IP in the treatment of mild to moderate COVID‐19. It includes 416 symptomatic patients with confirmed SARS‐CoV‐2 infection. In addition to a defined standard of care, patients  randomly (1:1) receive either IP 500 mg tablet (IP group) or a matching placebo (placebo group) at 50 mg kg −1 body weight/day rounded to the nearest 500 mg dose (maximum 4 g day −1 ) administered in 3–4 divided doses for 10 days. Compared to the placebo group, IP group shows significantly higher rates of clinical response (CR) and clinical cure (CC) on Day‐6 for both non‐hospitalized patients and the total population. IP group shows significantly earlier CR and CC with fewer adverse events and no mortality. Based on these findings and the fact that IP increases natural killer cell‐mediated cytotoxicity of virus‐infected cells as an early immune response to viral infection and enhances NKG2D ligand expression, it is concluded that IP should be started early to maximize the benefit in mild to moderate COVID‐19 patients. (Trial registration number: CTRI/2021/02/030892).