3-methyl-4-(2-arylhydrazono)-1H-pyrazol-5(4H)-one were synthesized by condensation of aryl diazonium chloride with 3-methyl-1H-pyrazol-5(4H)-one. The ligands were characterized by elemental and spectral analysis. Complexes of these ligands were synthesized using Cu(II) and Ni(II) metal ions. The structural studies of complexes were carried out using different techniques such as electronic spectra, infrared spectra, conductivity and magnetic moment-measurements, ESR and XRD spectral study. The elemental analysis, magnetic moments and spectral data authenticates the monomeric nature with high spin octahedral geometry to these complexes.