Abstract: The interactions of transition metals cobalt(II) and nickel(II) ions with the amino acids L-threonine(L-thr), L-proline(L-pro) and L-lysine(L-lys) in aqueous solution have been studied by using visible spectroscopic method. On addition of amino acids to the aqueous solution of the metal ions, a change in the visible spectra is observed due to the replacement of the water molecules from the coordination sphere of the aquo-complex [M(H2O)6]2+ by the amino acid molecules.