The stability constants of Mn(II), Fe(III), Co(II), Ni(II), Cu(II) and La(III) metal ions with 2-((4-morpholinobenzylidene)amino)phenol (HL) were determined in 25 % (v/v) ethanol-water medium at 25 oC (I = 1 M NaClO4). The calculations of the metal-ligand stability constants were obtained by Calvin-Bjerrum pH-metric method using the Miniquad-75 computer program. The dissociation constant (pKa) value of monoprotic ligand HL was found as 10.36. The order of the formation constant values (log Ki) of metal ion complexes with HL increases in the order La(III) > Fe(III) > Cu(II) > Co(II) > Ni(II) > Mn(II). Optimization of the geometries of the HL metal complexes was done with the density functional theory method (DFT) using the Gaussian 09 program package as DFT methods.