In this paper, an ultrasensitive and highly selective analytical method for the voltammetric determination of the anti-inflammatory drug mesalazine (MES) at the Co-exchanged mordenite/mesoporous carbon modified glassy carbon electrode (Co-MOR/MC-GCE) is presented. The combination of unique properties of zeolite and mesoporous carbon, affirmed by conducting morphology and textural parameters studies, resulted in the fabrication of the unique platform sensing, which exhibited a significant enhancement effect of MES oxidation peak current. In the voltammetric determination of mesalazine by the means of differential pulse voltammetry (DPV), univariate optimization stage of the instrumental parameters and the pH value of the supporting electrolyte was performed. In 0.04 mol L⁻¹ Britton-Robinson buffer solution (pH 2.0), the oxidation peak of MES at 0.41 V vs. Ag | AgCl | 3 M KCl reference electrode revealed a linear response in the range of 0.99 – 99.01 µg L⁻¹ (6.47·10⁻⁹ – 6.47·10⁻⁷ mol L⁻¹) with the limit of detection (LOD) equal to 0.27 µg L⁻¹ (1.76·10⁻⁹ mol L⁻¹). The developed protocol was successfully applied for the direct determination of mesalazine in pharmaceuticals, environmental waters, and biological fluids (human urine and serum) with recovery of 103.4 – 119.3%.