A novel series of pyrazol-4-yl-1,2,4-triazole-3-thiol derivatives 14a-l was designed, prepared and characterized by many spectroscopic techniques. All the novel compounds were screened for their anti-proliferative activity towards breast cancer cell line (MCF-7), colon cancer cell line (HT-29) and lung cancer cell line (A-549) utilizing celecoxib, erlotinib and osimertinib as standards. Compounds 14b, 14g and 14k were the most active towards HT-29, MCF-7 and A-549 cell lines, sequentially with IC