The required starting material 3-(2-(4-substitutedphenyl)-hydrazono)-pentane-2, 4-dione (2a-b) was synthesized from 4-substitutedaniline reacted with acetyl acetone. The compound (2a-b) react with hydrazine hydrate and phenyl hydrazine to give 4-((4-substitutedphenyl)-diazenyl)-3,5-dimethyl-1H-pyrazole (3a-b) and 4-((4-substituted phenyl)-diazenyl)-3,5-dimethyl-1-phenyl-1H-pyrazole (4a-b) respectively. 1-(4-((4-substitutedphenyl)-diazenyl)-3,5- dimethyl-1H-pyrazol-1-yl)-ethanone (5a-b) has been synthesized by the treatment of 4-((4-substitutedphenyl)- diazenyl)-3,5-dimethyl-1H-pyrazole (3a-b) with acetyl chloride in pyridine. The newly synthesized compounds were characterized by analytical and spectral studies. All the synthesized compounds were evaluated for antimicrobial activity. Some of these compounds show moderate antimicrobial activity as compared to the known reference drug ciprofloxacin.