Abstract: A seed disinfectant composition comprising(A) (E)-1-(2,4-dichlorophenyl)-4,4-dimethyl-2-(1,2,4-triazol-1-yl)-1-penten-3- ol containing not less than 50% by weight of (-)-(E)-1-(2,4-dichlorophenyl)-4,4-dimethyl-2-(1,2,4-triazol-1-yl)-1-pente n-3-ol and(B) At least one benzimidazole thiophanate fungicide and optionally comprising(C) O,O-dimethyl-O-(2,6-dichloro-4-methylphenyl)phosphorothioate and/or(D) 1-Ethyl-1,4-dihydro-6,7-methylenedioxy-4-oxo-3-quinoline carboxylic acid or a salt thereof are disclosed. The seed disinfectant composition of the present invention exhibits a synergistically high preventing effect on various seed born diseases and simultaneously has a wide antifungal spectrum and shows a stable preventing effect on the fungi having resistance to conventional disinfectants.