A series of pyrazolines were synthesized by Michael addition of chalcones with hydrazine hydrate in the presence of sodium acetate under conventional heating and microwave irradiation. The structures of the newly synthesized chalcones and pyrazolines were established based on IR, H-1- and C-13-NMR and mass spectral data. All the synthesized compounds were screened for their antimicrobial activity. Some of the compounds showed very good activity compared to standard drugs against all pathogenic bacteria and fungi.