Two Schiff bases, 4-[(2-hydroxynaphthalen-1-yl)methylidene]amino}-1,5,-dimethyl-2-phenyl-1,2-dihydro-3H-pyrazol-3-one (APNA) and 4-[(2,3-Dihydroxybenzylidene)amino]-1,5-dimethyl-2-phenyl-1,2-dihydro-3H-pyrazol-3-one (SBAP) derived from 4-aminoantipyrine are reported. The compounds were recrystallized in methanol and characterized using spectroscopic techniques (IR, NMR) and single-crystal X-ray diffraction analysis. The XRD structure shows that APNA and SBAP crystallize respectively in the orthorhombic and monoclinic crystal systems, space groups of Pna2(1) and C2/c, and both has Z = 8 in the unit cells. SBAP has all trans configuration around its central C=N double bond. It is stabilized by C18-H18 center dot center dot center dot N2 and C7-H7 center dot center dot center dot O3 intramolecular hydrogen bonds. The presence of distinctive bond length of N3-C12 in APNA and C=N (1451 cm(-1)) stretching vibration in the IR spectrum of SBAP are evidence that the Schiff bases formed. Additional hydroxyl group in SBAP raised the TPSA (146.478 angstrom(2)) more than APNA's (83.087 angstrom(2)) which had more aromatic ring (increased conjugation) and lesser number of hydroxyl group. The computed molecular descriptors of APNA and SBAP suggest that pyrazolones will have no pharmacokinetic challenge if developed as drug.