Two new Schiff base ligands 4-[(1E)-(3,4-dimethoxyphenyl)methylene]amino-1,5-dimethyl-2-phenyl-1,2-dihydro-3H-pyrazol-3-one (1) and 4-[(1E)-(2-hydroxy-5-methoxyphenyl)methylene]amino-1,5-dimethyl-2-phenyl-1,2-dihydro-3H-pyrazol-3-one (2) have been prepared and characterized using elemental analysis, UV-vis, FT-IR, 1H and 13C NMR spectroscopy, and X-ray crystallographic technique. Tautomeric equilibria (phenol-imine, O-H...N and keto-amine, O...H-N forms) have been studied by using UV-vis absorption spectra for the compound 2 in some solutions. Crystal structure analyses showed that the title molecules 1 and 2 crystallize in the monoclinic space group P21/c and P21 with the unit cell parameters: a = 12.5665(3) Å and 5.6666(2) Å; b = 10.4791(2) Å and 12.2444(5) Å; c = 14.6240(3) Å and 12.1556(4) Å; V =1820.65(7) Å3 and 826.84(5) Å3; Dx = 1.282 g.cm-3 and 1.355 g.cm-3; and Z = 4 and 2, respectively.