The use of ribavirin in influenza treatment is a matter of debate. Due to adamantine- and oseltamivir-resistant strains of the current pandemic H1N1 (pdmH1N1) influenza viruses, the demand for alternative antiviral treatments has increased. This study demonstrated the potent antiviral effects of ribavirin in a mouse model of pdmH1N1 influenza infection (A/Mexico/4108/2009). It was found that treatment with 40 mg ribavirin kg⁻¹ day⁻¹ partially protected the animals if initiated immediately upon infection. Administration of similar concentrations on subsequent days or immediate therapy with lower doses efficiently delayed disease progression. Correlation studies showed a direct relationship between low viral titres in the lung during the early stages of infection with animal survival in ribavirin-treated animals. Reduced lung pathology in animals treated with ribavirin following infection also indicated the importance of immediate treatment. This study revealed the antiviral properties of ribavirin and these results justify comprehensive clinical studies for the use of ribavirin against influenza virus in future outbreaks.