New series of (4E)-4-[(2-chloro/hydroxy quinolin-3-yl) methylidene]-2-substituted-5-methyl-2,4-dihydro-3H-pyrazol-3-ones derivatives were synthesized by the condensation of substituted 5-methyl-2,4-dihydro-pyrazol-3-ones with 6/8-substituted-2-chloro/hydroxy quinoline-3-carbaldehydes. The novel compounds were confirmed by Mass, NMR and IR spectroscopy and were also screened for their antimicrobial activities. Among them a few of the novel compounds showed tremendous bioactivities comparable with that of standard drug.