A new series of 1-Acetyl-5-(4-nitrophenyl)-3-(2-thienyl/pyridinyl/phenyl)-2-pyrazoline were synthesized by reacting 3-(4-nitrophenyl)-1-(2-thienyl/pyridinyl/phenyl)-2-propene-1-one (chalcones) with hydrazine hydrate in acetic acid. All the prepared compounds were characterized by spectral data (IR, 1 H NMR) and microanalysis. All the synthesized compounds were also evaluated for their antibacterial activity against Gram +ve and Gram-ve bacteria.