Biguanide (C₂H₇N₅) is a bidentate ligand, and its derivative piperazinedibiguanide (C₈H₁₈N₁₀) is a nitrogen-donor tetradentate ligand. The tetradentate ligand was synthesized and complexed with Cu(II) by reacting it with copper(II) salts. Elemental analysis, magnetic measurements, and spectral studies confirmed the complexes’ paramagnetic, square planar nature.Antifungal activity was evaluated against Aspergillus niger and Aspergillus versicolor using the disc dilution method on Potato Dextrose Agar and Sabouraud Dextrose Agar at 400, 200, and 100 µg/ml. All complexes showed over 80% inhibition at 400 µg/ml. The copper piperazinedibiguanide hydroxide complex achieved 100% and 99.10% inhibition of A. versicolor on PDA and SDA, respectively. These results support further study of the antifungal potential of similar transition metal complexes