New hybrids of tetrazole moiety with different chalcone derivatives were synthesized. The reaction of these chalcones with hydrazine hydrate resulted in the formation of tetrazole-pyrazoline hybrids. Evaluation of the in vitro antiproliferative activity of all newly synthesized hybrids against three cancer cell lines and Vero-B normal cell line, using MTT-based assay, was performed. Most of the chalcone derivatives exerted superior activity against colon HCT-116 and prostate PC-3 cell lines, in comparison with cisplatin (IC50= 20 and 5 μg/ml) and 5-FU (IC50= 17.3 and 21.4 μg/ml), respectively. Compound 5a was found to be the most active antiproliferative agent against colon HCT-116 and prostate PC-3 cell lines (IC50= 0.6 and 1.6 μg/ml) with high selectivity indices (SI= 6.66 and 2.50), respectively. Compound 8f, in particular, displayed a wider spectrum of activity that included, in addition, excellent effect against breast MCF-7 cell lines with SI= 2.75. The available docking results revealed a good binding of 5b with HDAC2 and CYP17A1 that endorses the in vitro biological activity against the tested colon and prostate cell lines.