Abstract Influenza occurs with seasonal variations and reaches the peak prevalence in winter causing the death of many people worldwide. A few inhibitors of viral neuraminidase, including amantadine, rimantadine, zanamivir, and oseltamivir, have been used as influenza therapy. However, as drug-resistant influenza viruses are generated rapidly, there is a need to identify new agents for chemotherapy against influenza. Therefore, research on more effective drugs has been given high priority. During the course of an anti-influenza screening program on natural products, two new compounds ( 1 and 2) along with seven known flavonoid derivatives ( 3– 9) were isolated as active principles from an EtOAc-soluble extract of the root bark of Erythrina addisoniae. The stilbenoid ( 2) and chalcone ( 3, 4, and 6) compounds of the isolates exhibited stronger activity than the isoflavone ones. Compound 2, which is a formylated stilbenoid derivative, exhibited strong inhibition of both influenza H1N1 and H9N2 neuraminidases with IC 50 values of 8.80 ± 0.34 μg/mL and 7.19 ± 0.40 μg/mL, respectively.