The title compound, 5-(4-Chlorophenyl)-1-(6-methoxypyridazin-3-yl)-1H-pyrazole-3-carboxylic acid, has been characterized by using elemental analysis, MS, FT-IR, H-1 NMR and C-13 NMR spectroscopic, and crystallographic techniques. The title compound crystallizes in the triclinic space group P-1 with a = 9.612(1), b= 9.894(1), c = 17.380(1)angstrom, alpha = 90.213(5)degrees, beta= 104.99(1)degrees, gamma = 111.072(5)degrees, V= 1481.3(2) angstrom(3) and D-x= 1.483 g cm(-3) respectively. The structure of the compound has also been examined by using quantum chemical methods. The molecular geometry and vibrational frequencies of monomeric and dimeric form of the title compound in the ground state have been calculated by using the B3LYP/6-31G(d,p) level of the theory. The calculated results show that the optimized geometry and the theoretical vibration frequencies of the dimeric form are good agreement with experimental data. In addition, HOMO-LUMO energy gap, molecular electrostatic potential map, thermodynamic properties of the title compound were performed at B3LYP/6-31G(d,p) level of theory. (C) 2014 Elsevier B.V. All rights reserved.