An antimicrobial protein, designated WjAMP-1, was purified from leaves of Wasabia japonica L. WjAMP-1 showed antimicrobial activity against both fungi and bacteria. The deduced amino acid sequence of cDNA of WjAMP-1 showed 60% and 70% identity with a hevein from Hevea brasiliansis and a hevein-like protein from Arabidopsis thaliana, respectively. However, matured WjAMP-1 lacked the hevein domain and may correspond to the C-terminal domain of hevein. Southern blot analysis showed that one or two copies of the WjAMP-1 gene were presented in the genome of wasabi. Expression of WjAMP-1 was detected in all organs tested, and was especially strong in petioles. Expression of WjAMP-1 was induced by the inoculation with fungal pathogens and treatment with methyl jasmonate. Recombinant WjAMP-1 expressed in Nicotiana benthamiana using potato virus X vector also inhibited not only growth of fungi but also bacteria. These results suggest that WjAMP-1 may be the C-terminal domain of hevein and one of the defense gene in W. japonica. WjAMP-1 gene may be useful genes to generate resistant plants against fungal and bacterial pathogens.