Synthesis of some new oxomolybdenum(V) and dioxomolybdenum(VI) complexes with a Schiff base isonicotinioyl(5-bromo-2-hydroxybenzylidene)hydrazide (L) derived from 5-bromosalicylaldehyde and isonicotinoylhydrazide are reported. The complexes have been characterized by elemental analyses, molar conductance, magnetic susceptibility data, IR, UV-Vis, EPR, H-1 NMR, and FAB mass spectral studies. The physicochemical studies and spectral data indicate that L acts as a monovalent tridentate chelating agent. The FAB mass and X-band EPR spectra indicate that the pentavalent Mo in the complex is monomeric in nature. The X-ray diffraction studies of the complex [MoO(L)Cl-2] (I) correspond to the orthorhombic crystal lattice with the unit cell dimensions a = 16.11, b = 12.20, and c = 7.5 . The electrochemical behavior of the complex was investigated by cyclic voltammetry. All the complexes are found to be neutral with the distorted octahedral geometry. The thermal properties of the complex I were investigated by thermogravimetric techniques. The ligand L and the complexes I and [MoO2(L)Cl] (II) were screened for their in vitro antimicrobial activity. The complexes exhibited higher activity than L. The 3D molecular modeling and analysis for bond length and bond angles have also been carried out for complex I.