A new series of 5-chloro-3-(4-substituted anilino)-2-phenyl-2,3-dihydro-1,2λ5-benzoxaphosphol- 2-ones 4a-j have been prepared via Mannich type reaction by reacting 5-chlorosalicyaldehyde 1 with phenyl dichlorphosphine 2 and aromatic amines 3a-j in anhydrous benzene under reflux condition. Their chemical structures were characterized by using 1H, 13C, 31P and mass spectral studies. All the title compounds were screened for antioxidant properties by radical scavenging methods such as 1,1-dipheyl-2-picryl hydrazyl (DPPH), Reducing power and H2O2 scavenging methods. They exhibited potent in vitro antioxidant activity dose dependently. Their bioassay showed that they possess significant antibacterial activity.