The reaction of 1-(2,5-dimethylphenyl)-3-phenylthiourea (L) and copper(II) chloride dihydrate resulted in production of the complex [CuL₂Cl] which contains monovalent copper. The complex was isolated in the monoclinic crystal system (space group = C 1 2/c 1) and its coordination geometry is trigonal planar composed of one chlorine and two sulfur atoms. The complex (150 µg/mL) provided significant inhibitory activity (40.5 mm) against the phytopathogen Fusarium oxysporum and led to complete inhibition of F. oxysporum-induced pathogenicity to wheat seeds. Percentages of wheat germination, evidence of phytotoxicity levels, were investigated: [CuL₂Cl] (150 µg/mL) offered percent germination of 67%, but the ligand was less toxic offering percentage of germination of 77%. Reduction in shoot lengths (control = 41 mm) and root lengths (control = 54.3 mm) of germinated wheat seeds influenced by our compounds was cleared. At 150 µg/mL, 1-(2,5-dimethylphenyl)-3-phenylthiourea, copper(II) chloride dehydrate, and [CuL₂Cl] offered shoot lengths of 26.3, 9.6, and 29.3 mm and root lengths of 34.7, 0, and 26.6 mm, respectively.