Essential oil extracted from the leaves of Chenopodium ambrosioides Linn. (Chenopodiaceae) was tested against the aflatoxigenic strain of test fungus Aspergillus flavus Link. The oil completely inhibited the mycelial growth at 100 microg/ml. The oil exhibited broad fungitoxic spectrum against Aspergillus niger, Aspergillus fumigatus, Botryodiplodia theobromae, Fusarium oxysporum, Sclerotium rolfsii, Macrophomina phaseolina, Cladosporium cladosporioides, Helminthosporium oryzae and Pythium debaryanum at 100 microg/ml. The oil showed significant efficacy in inhibiting the aflatoxin B1 production by the aflatoxigenic strain of A. flavus. During in vivo investigation it protected stored wheat from different storage fungi for one year. Chenopodium oil also exhibited potent antioxidant activity when tested by ABTS method. All these observations suggest the possible exploitation of the Chenopodium oil as potential botanical fungitoxicant in ecofriendly control of post harvest biodeterioration of food commodities from storage fungi.