Herein, we describe the synthesis and characterization of a Schiff base ligand (E)-N'-(2-hydroxybenzylidene)-4-methoxybenzohydrazide (HBMB) and its Mn(II), Ni(II), and Cu(II) metal complexes (C1-C3) respectively. The ligand HBMB was synthesized by reacting condensation of salicylaldehyde and 4-methoxy benzohydrazide in a 1:1 molar ratio. The structure of HBMB and its metal complexes (C1-C3) were evaluated by using UV-Vis, FT-IR, 1H-NMR, mass spectroscopy as well as on the basis of elemental analysis, conductivity measurements, and thermogravimetric techniques (TGA). The synthesized molecules' tumoricidal properties were performed against human breast cancer (MCF-7) and colon cancer (HT 29) cell lines. The biological results indicated that the ligand, HBMB, and metal complexes possess dose-dependent selective cytotoxicity against the tested carcinoma cells. The synthesized compounds were further evaluated for their in vitro antimicrobial activities against Gram-positive bacteria (Staphylococcus aureus), Gram-negative bacteria (Escherichia coli), and fungal strains (Aspergillus niger).