Five herbicides commonly used in rapeseed crop, canola (Brassica napus var Olifera) fields in Iran were studied with an eye to their antifungal activities against six isolates of Trichoderma species and also the phytopathogenic fungus Sclerotinia sclerotiorum. The doses tested were the same as are recommended for applications in canola crops. The results showed that the dinitro aniline herbicides (trifluralin and ethalfluralin) had the highest antifungal activities in vitro on the toxified CDA media; also three other herbicides behaved differently in relation to the fungi investigated. Cycloxydim had the most toxicity against Trichoderma sp. and sethoxydim had the least deleterious effects. But, with, Sclerotinia sclerotiorum, sethoxydim had the most toxicity together with cycloxydim with an intermediate level of anti-fungal activity between sethoxydim and haloxy fop ethoxy ethyl. This may be the first global report of the antifungal activities of the haloxy fop ethoxy ethyl, ethanol fluralin and cycloxydim.