via an addition reaction, a tetrahedral cobalt(II) complex with the asymmetric ligand 1-(2,5-dimethylphenyl)-3-phenylthiourea (L) was synthesized. Crystal structure of the complex, [CoL₂Cl₂], demonstrated a monoclinic system packing and coordination of the divalent cobalt ion with S atoms of two thiourea ligand molecules and two chlorine atoms. Fusarium species are very destructive phytopathogens, causing considerable economic loss. Drawbacks of organic antifungals include their poor solubility, instability and limited bioavailability. Environmental accumulation and negative effects on people’s health are results of their extensive use. The complex [CoL₂Cl₂], comparing with its precursors, offered higher inhibitions in plates of three Fusarium phytopathogens, i.e. Fusarium lateritium, Fusarium oxysporum, and Fusarium solani. [CoL₂Cl₂] (150 µg/ml) inhibited F. oxysporum, F. solani, and F. lateritium by 28–38 mm, but 1-(2,5-dimethylphenyl)-3-phenylthiourea and cobalt(II) chloride hexahydrate inhibited these fungi by 7–8.5 and 7.5–24.5 mm, respectively. In the presence of [CoL₂Cl₂] (150 µg/ml), the percent pathogenicity to wheat seeds by F. oxysporum and F. lateritium was brought to zero (20% by F. solani). Phytotoxicity action of [CoL₂Cl₂], cobalt(II) chloride hexahydrate, and 1-(2,5-dimethylphenyl)-3-phenylthiourea (150 µg/ml) on wheat seed germination was weak, reducing the optimal germination percentage (100% for control) to 83.3, 76.7, and 90%, respectively.