A tridentate Schiff base ligand HL(ATS), N-[2-acetylthiophene]-salicylideneimine was  derived from the 1 : 1 condensation of 2-acetyl thiophene and 2-aminophenol was prepared and characterized by elemental analysis, FT-IR, Mass, ¹H-NMR, UV-VIS, thermogravimetric analysis and fluorescence spectra. Cobalt(II) complex was obtained by the reaction  of the Schiff base ligand (HL) with cobalt(II) hexahydrate in 1 : 1 molar ratio. The cobalt (II) complex have been characterized by elemental analysis, FT-IR, ¹H-NMR, Ms, UV-VIS, magnetic moment, molar conductance, thermogravimetric analysis (TGA) and fluorescence spectra. Elemental analysis (CHNS) data proved 1 : 1 (M : L) stoichiometry for the reported cobalt (II) complex. IR spectra showed that cobalt (II) complex was coordinated in metal ions via the imine N, O and S atoms. Magnetic and UV-VIS spectra, showed that the geometrical structure of cobalt(II) complex is an octahedral. The molar conductance data revealed that the cobalt(II) complex is non-electrolyte. Thermogravimetric analysis (TGA) revealed the high thermal stabilities.