The role of plant chitinases in protecting plants against a variety of fungal pathogens is well established. In the present study, a cDNA clone containing a class I chitinase (Chi-1) gene, designated as PgChi-1, has been isolated from the oriental medicinal plant Panax ginseng. PgChi-1 is predicted to encode a protein of 34.9 kDa consisting of 323 amino acid residues. PgChi-1 was found to be expressed constitutively in all of the studied organs of ginseng plant. Under various abiotic stress treatments including Cu, H2O2, mannitol, SA, JA, and NaCl, the expression of PgChi-1 in plantlets and hairy roots increased significantly compared to the control. When different parts of root were analyzed, maximum level was observed in taproot. In addition, levels of PgChi-1 expression were compared between healthy root and fungal, bacterial, and nematode infected root. Significant increase of PgChi-1 was noticed in pathogen infected roots than healthy roots. This study revealed that PgChi-1 may protect the P. ginseng under both biotic and abiotic stress conditions.