Pyrazole and their derivatives are found to have intense biological efficiency. In the present work some substituted pyrazole derivatives were synthesized and used as ligands (4‐[2‐vinylthiophene]‐3‐methyl pyrozolin‐5(4H) ‐ one (L1), 4‐[4‐chloro benzylidine]‐3‐methyl pyrozolin‐5(4H) ‐ one (L2) and 4‐[4‐dimethylnitro benzylidine]‐3‐methylpyrozolin‐5(4H) ‐ one (L3)) to prepare the zirconium (IV) complexes. The synthesized ligands and their complexes were obtained as colored powdered materials and were characterized using magnetic measurements, melting point, molar conductance, infrared, electronic, 1HNMR, mass spectra and thermogravimetric analyses. All of the tested compounds showed good microbial activity against pathogenic microorganisms. The tested compounds exhibited considerable antitumor activity and cytotoxic specificity towards human colon carcinoma cell line (HCT‐116).