A new series of pyrazoles have been synthesized via 2-(3-phenyl-1,3,4,5,6,7-hexahydro-2H-indazol-2-yl)thiazol-4(5H)-one(2), which on treatment with phosphorus pentachloride and phosphoryl chloride afforded 4-chlorothiazole derivative(3). Reaction of 3 with hydrazine hydrate in boiling gave 4- hydrazineylthiazole derivative (4). Heterocyclization of 4 with aromatic aldehydes and active methylene compounds afforded the pyrazole derivatives (5-8). The synthesized pyrazoles (5–8) and their precursor (1–4) were evaluated for antimicrobial activities. All prepared compounds revealed abroad-spectrum antimicrobial activity with maximum inhibition activity against Streptococcus mutans. Compound 3 revealed the most potent antibiofilm inhibition activity against the three used pathogens. Additionally, all compounds (1-8) were also tested for cytotoxic activity against hepatoma and colon carcinoma cell lines. Compounds 3, 5 and 7 displayed good to excellent activity against all tested tumor cells with IC50 values ranged from 6.13 to 23.85 μg/ml. On the other hand, all compounds were evaluated for cytotoxic activity on normal human melanocytes cell lines and found to be signified its high selectivity toward cancer cells than normal cells. Moreover, the molecular modeling study was carried out using (MOE 2014) software. The computational studies are confirming the results in biological activity.