We report the synthesis, structural characterization and thermal behavior of N'-(4-chlorobenzoyl)-N, N-di-n-butylthiourea (HL) and its nickel complex (NiL2)-Some physical properties of the prepared compounds were investigated using elemental analyses, IR, H-1-NMR, and magnetic susceptibility. The molecular structures of HL and NiL2 were determined by single crystal X-ray diffraction. HL is a monoclinic, space group P2(1)/c with a = 10.7457(5) b = 15.5909(8) angstrom, c = 10.4536(5) angstrom, beta = 104.398(1)degrees, and V = 1696.34(14) angstrom(3) with Z = 4 for d(calc) 1.280 g/cm(3). NiL2 is a triclinic, space group P-1 with a = 8.561(3) angstrom, b = 16.643(6) angstrom, c = 25.723(9) angstrom, alpha = 77.448(6)degrees, beta = 84.077(7)degrees, gamma = 88.684(6)degrees, and V = 3558(2) angstrom(3) with Z = 4 for D-calc = 1.326 g/cm(3). The ligands coordinate to the metal atom in a bidentate manner, yielding an essentially neutral complex of the type ML2. Thermal decomposition of related compounds was investigated by TG and DTA. The pyrolytic end product was identified by X-ray powder diffraction.