4-Carboxaldehyde-1-phenyl-3-methyl-2-pyrazolin-5-one condensed with phenylhydrazine to form ligand (HL). These metal complexes are of type [ML2 (H2O)2] (M = Mn, Co, Ni and Cu). Elemental analysis, magnetic susceptibility, electrical conductance, electronic and infrared data suggest octahedral structure for the metal complexes. All the compounds were tested for their antibacterial activity. The result indicates that the growth of the tested organisms was inhibited by most of the compounds.