Abstract A novel, environmentally considerate electroanalytical sensor was developed for the determination of vonoprazan fumarate (VON) through modification of a carbon paste electrode with biomass-derived carbon quantum dots (CQDs), representing a sustainable, defect-rich, and effective alternative to conventional CQD-based sensors that rely on synthetic materials and complex fabrication. The CQDs were synthesized from pecan nut ( Carya illinoinensis ) using a microwave-assisted solvothermal approach and exhibited abundant functional groups and quantum confinement effects, as confirmed via X-ray photoelectron spectroscopy (XPS) in combination with Fourier-transform infrared (FTIR) spectroscopy, fluorescence spectroscopy, ultraviolet–visible spectroscopic approach (UV–Vis), transmission electron microscopy (TEM) and scanning electron microscopy combined with energy-dispersive X-ray spectroscopy (SEM–EDX). Electrochemical impedance spectroscopy (EIS) revealed enhanced interfacial electron-transfer kinetics and electrocatalytic activity, highlighting the enhanced electrode performance of the CQD-modified sensor and its direct contribution to improved sensitivity and selectivity. Quantitative determination of VON was performed using differential pulse voltammetry (DPV), achieving a limit of detection of 0.39 nM, a limit of quantification of 1.19 nM, and a linear response over 10–100 nM (R 2 = 0.9992). The method met international validation criteria for accuracy, precision, and robustness, and was successfully applied to pharmaceutical preparations, spiked human plasma samples, and laboratory-prepared industrial wastewater. This work addresses the growing demand for sensitive, reliable, and eco-friendly detection of pharmaceutical analytes, providing a versatile, sustainable, and effective sensing platform.