5-substituted phenylazo salicyaldehyde derivatives have been prepared by diazotization of aromatic primary amines and condensing them with salicyldehyde on treatment with hydrazine hydrate in ethanol, furnished the 5-substituted phenyl azo salicyldehyde hydrazone. This hydrazone on reaction with 4-benzylidene-2-phenyl oxazolinone in presence of pyridine gives 1-[(2-hydroxy-5-substituted phenyl azo)-benzylidene amino]-2-phenyl-4-benzylidene- 5-oxo imidazoline. The newly synthesized compounds were characterized on the basis of elemental analysis and 1H NMR, IR spectral data. The synthesized products have been evaluated for their antimicrobial activity against gram positive and gram negative bacteria. Some of the products exhibited comparable activity with known standard drugs at same concentration.