A novel Schiff base ligand (L), namely (E)-N-(1-(2,4,5-trimethylphenyl)ethylidene)-1H-1,2,4-triazol-3-amine, derived from a substituted phenolic precursor, and its copper(II) complex were successfully synthesized and characterized using various spectroscopic techniques, including FTIR, NMR, and elemental analysis. Spectral investigations confirmed the coordination of the ligand to the Cu(II) ion through the azomethine nitrogen and phenolic oxygen atoms, indicating bidentate chelation and the formation of a stable metal complex. The antimicrobial activity of the synthesized compounds was evaluated against Escherichia coli using the agar well diffusion method. The Cu(L)₂ complex exhibited significantly enhanced antibacterial activity compared to the free ligand, as evidenced by larger zones of inhibition. A concentration-dependent increase in inhibition diameter was observed, demonstrating improved efficacy at higher concentrations. The enhanced biological performance of the metal complex can be attributed to chelation-induced increases in lipophilicity, which facilitate better penetration through the bacterial cell membrane, along with possible metal-mediated interference in essential cellular processes. In addition to its antimicrobial properties, the Cu(L)₂ complex was investigated as an electrochemical sensing material for the detection of Naproxen (NPR). The modified electrode exhibited a linear response over the concentration range of 1–10 μM, demonstrating excellent sensing capability toward the target analyte. The sensor showed a sensitivity of 0.13 μA μM⁻¹ and achieved a limit of detection (LOD) of 1 μM. The enhanced electrochemical performance is attributed to the redox-active Cu(II) center and the efficient electron-transfer characteristics of the Schiff base framework, which promote rapid and sensitive analyte detection.