Respiratory syncytial virus (RSV) and influenza A virus (IAV) are two of the most common viruses that cause substantial morbidity and mortality in infants, young children, elderly persons, and immunocompromised individuals worldwide. Currently, there are no licensed vaccines or selective antiviral drugs against RSV infections and most IAV strains become resistant to clinical anti-influenza drug. Here, we described the discovery of a series of 2-((1H-indol-3-yl)thio)-N-phenyl-acetamide as novel and potent RSV and IAV dual inhibitors. Thirty-five derivatives were designed, prepared, and evaluated for their anti-RSV and anti-IAV activities. Among the tested compounds, 14'c, 14'e, 14'f, 14'h, and 14'i exhibited excellent activity against both RSV and IAV, which showed low micromolar to sub-micromolar EC values. Further, compounds 14'c and 14'e were identified as the most promising dual inhibitors with lesser cytotoxicity than the clinical drug, ribavirin. These findings may contribute to the development of a lead compound for the treatment of RSV and/or IAV infections.