Abstract: Gardenia jasminoides E. (Rubiaceae) methanol extracts showed the highest level of antifungal activity against Pleurotus ostreatus, a wood-rotting fungus, compared to five other methanol plants extracts; [Thuja orientalis L. (Cupressaceae), Datura innoxia (Solanaceae), Ligustrum japonicum T. (Oleaceae), Juniperus chinensis var. procumbens (Cupressaceae) and Mallotus japonica M. (Euphorbiaceae)] and selected for further analysis. Two antifungal compounds were isolated from n-butanol and ethyl acetate solubles in the methanol extracts of Gardenia jasminoides leaves and stems by bioassay-guided fractionation, using Pleurotus ostreatus. The antifungal compounds found for the first time in Gardenia jasminoides against Pleurotus ostreatus were identified as genipin and geniposide based on instrumental analyses. Both also had potent inhibitory effects on two plant pathogenic fungi; Fusarium oxysporum and Corynespora cassiicola.