Circulation of avian influenza A viruses in poultry is a public health concern because these viruses may cause severe disease in humans and have the potential to become more transmissible among humans. Monitoring the susceptibility of these viruses to antivirals is important for influenza pandemic preparedness. However, information about their antiviral susceptibility is limited. Here, we determined the susceptibilities of avian influenza A(H5N1), A(H5N2), A(H5N8), A(H7N7), A(H7N9), A(H9N1), and A(H9N2) viruses isolated in Japan to the antivirals approved for use there: the M2 inhibitor amantadine; the neuraminidase inhibitors oseltamivir, peramivir, zanamivir, and laninamivir; and the RNA polymerase inhibitors baloxavir and favipiravir. Genotypic methods that detect amino acid substitutions associated with antiviral resistance and phenotypic methods that assess viral susceptibility to drugs revealed that these avian influenza A viruses are susceptible to neuraminidase inhibitors and RNA polymerase inhibitors. These results suggest that the neuraminidase inhibitors and the RNA polymerase inhibitors currently approved in Japan could be a treatment option against influenza A virus infections in humans.