The ligand 3,5-di-tert-butyl-2-hydroxy-N'-((2-oxo-1,2-dihydroquinolin-3-yl)methylene)benzohydrazide (H₂L) and its Co(II), Ni(II), Cu(II), Zn(II) complexes were synthesized. The ligand and its complexes were characterized by various spectro-analytical techniques including IR, ¹H NMR, ¹³C NMR, EPR, electronic spectroscopy, and elemental analysis. In addition, the molecular structures of H₂L, [Co^II(HL)₂] (1), [Ni^II(HL)₂] (2), [Cu^II(HL)(Cl)(CH₃OH)] (3), and [Cu^II(HL)(H₂O)(CH₃OH)].ClO₄ (4) were unambiguously established using single-crystal X-ray structure determination. However, the Zn(II) complex was characterized based on the IR, NMR and elemental analysis and the 6-coordinate with a 1:2 (M:L) ratio was proposed with the molecular formula [Zn^II(HL)₂)] (5). The synthesized compounds were investigated for antimicrobial and antitubercular activities. The copper(II) complex 4, has shown the lowest MIC of 0.4 µg/mL, against the gram-positive S. Aureus microorganism, which was better than the ligand and the standard Ciprofloxacin drug. Except for the complex 3, the ligand and rest of its complexes exhibited better activity against gram-negative, E. Coli with the MIC values ranging from 0.4 − 0.8 µg/mL and were much better than the standard Ciprofloxacin drug