Synthesis of cis (E)-1-(5-hydroxy-3-methyl-1-phenyl-1H-pyrazol-4-yl)-3-phenyl/aryl/heteroarylprop-2-en-1-ones from 1-phenyl-3-methyl-4-acetylpyrazol-5-one was achieved in good yield. s-cis (E)-1-(5-Hydroxy-3-methyl-1-phenyl-1H-pyrazol-4-yl)-3-arylprop-2-en-1-ones were isomerized to s-trans (E)-4-(3-(phenyl/aryl/heteroaryl)acryloyl)-5-methyl-2-phenyl-1H-pyrazol-3(2H)-ones using iodobenzene diacetate in dichloromethane at room temperature in excellent yield. The structure and geometry of these 𝛼, 𝛽-unsaturated ketones (pyrazolyl ketones) were established with the help of NMR, 2D NMR and HRMS techniques. The cytotoxicity of pyrazolyl chalcones showed that s-cis (E) 1-(5-Hydroxy-3-methyl-1-phenyl-1H-pyrazol-4-yl)-3-(4-methylphenyl)-prop-2-en-1-one is active at very low concentrations (IC50 13.3 𝜇M) against colon cancer cell line (HCT-116). The in vitro anti-microbial studies of pyrazolyl chalcones were also tested against grampositive (B. subtilis, S. aureus) and gram-negative bacteria (E. coli) and for anti-fungal activity against C. albicans and A. niger.