In the present study, new Co(II), Ni(II) and Cu(II) complexes were synthesized from the reaction of tetradentate Schiff's base ligand (H2L)= (N, N'-(pyridine- 2,6- diyl) bis (2- (((Z)- (2- hydroxynaphthalen-1-yl) methylene) amino) benzamide that was synthesized via condensation of 2-amino-N-{2-[(2-amino-benzoylamino) pyridine]-benzamide} with 2-hydroxy-1-naphthaldehyde. The ligand and its metal (II) complexes were characterized by microanalyses, magnetic, spectral, powder X-ray diffraction (XRD) and thermal studies. An octahedral geometry has been proposed for [Co(L)(H2O)2].3H2O (1), [Ni(L)(H2O)2].1½H2O (2) and square planar for [Cu(L)](3) and [Cu(H2L)(OH)Br](4). EPR spectra of Cu(II) complexes are consistent with d x²-y² ground state. 3D molecular modeling studies have been carried out for ligand and complex (1). Average crystallite size (D) and dislocation density (δ) were calculated from XRD. All compounds were screened for their in vitro antioxidant activity. The results showed that the ligand possesses excellent activity compared to the reference (Ascorbic acid drug) and complex (4) was the most potent one. Moreover, the current compounds were tested for their antimicrobial activity.