Abstract: To clarify the potential application of cinnamon essential oil as a botanical fungicide, its antifungal activities against four important pathogenic fungi from vegetables and fruits were tested in vitro and in vivo. The results indicated that the mycelial growths of Botrytis cinerea, Penicillium expansum, Ahernaria alternate and Fusarium oxysporum f. sp. cucumaium were inhibited to varying degrees by cinnamon oil and the EC₅₀ values were 272.17, 324.78, 316.24 and 326.95 mg/L, respectively. In addition, the cinnamon oil could inhibit the spore germination of B. cinerea, P. expansum, A. alternate and F. oxysporum, and the corresponding EC₅₀ values were 196.01, 273.52, 390.44 and 311.23 mg/L. The protective and therapeutic efficacies of cinnamon oil against B. cinerea were 64.16% and 34.90% (3 d) on the tomato treated with 10 mg /mL concentration respectively. However, its protective efficacy was not significantly different with the control fungicide (procymidone) at 1 g/L.