The new copper complex, [Cu(HL)(OH2)2](NO3), including the tridentate N-acyhydrazone derived from 4-hydroxy-benzohydrazide and 2-hydroxy-3-methoxybenzaldehyde, (H2L), has been synthesized and characterized in the solid state and in solution by spectroscopic (FTIR, Ra, UV–vis, EPR) methods. The results were compared with those obtained for the hydrazone ligand and complemented with computational methods based on DFT. The crystal structure of the complex has been determined by X-ray diffraction. It crystallizes in the triclinic space group with Z = 2. The Cu(II) ion is in a distorted square pyramidal environment, coordinated to a planar HL- anion acting as a tridentate ligand. The 5-fold coordination is completed with two water molecules. It is arranged in the lattice as H-bonded ribbon-like polymers that extends along the [1 2 1] crystal direction. The cytotoxicity of the complex together with that of the H2L ligand and the copper ion were evaluated in vitro against five different human cancer cell lines namely A549 (lung), MG-63 (bone), MCF-7 and MDA-MB-231 (breast) and Jurkat (leukemia). The copper complex inhibits the cell viability in a dose dependent manner with a greater potency than the H2L ligand and the free copper ion displaying even higher antitumor activity than the well-known anticancer metallodrug cisplatin.