Influenza A virus infection causes a contagious respiratory illness that poses a threat to human health. However, there are limited anti-influenza A therapeutics available, which is further compounded by the emergence of drug resistant viruses. In this study, Sophora quinolizidine alkaloids were identified as a new class of anti-influenza A virus agents. Among the tested Sophora alkaloids, dihydroaloperine exhibited the most potent activity with an EC50 of 11.2 muM. The potency of the quinolizidine alkaloids was improved by approximately 5-fold with chemical modifications on the aloperine molecule. These compounds were effective against an H1N1 influenza A virus that was resistant to the two antiflu drugs oseltamivir and amantadine. The identification of the quinolizidine alkaloids as effective and novel anti-influenza A agents may aid in the development of new therapeutics.