<p>In this study, phosphorus-doped graphitic carbon nitride (PGCN) was integrated into a glassy carbon electrode (GCE) to facilitate the electrochemical detection of ofloxacin (OFX). The modified sensor exhibited enhanced sensitivity and selectivity for ofloxacin detection. PGCN was synthesized via a one-step thermal polymerization of melamine and ammonium phosphate. Various analytical techniques such as X-ray diffraction (XRD), scanning electron microscopy (SEM), high-resolution transmission electron microscopy (HRTEM), and X-ray photoelectron spectroscopy (XPS) were used to characterize the PGCN/GCE. Electrochemical impedance spectroscopy (EIS), differential pulse voltammetry (DPV), and cyclic voltammetry (CV) were used to assess the electrochemical activity of ofloxacin using PGCN. The results indicated that the PGCN/GCE modification significantly improved the electron transfer rate and provided more active sites, resulting in a lower detection limit of 5.81&#xa0;µM and a broader linear range (5–120&#xa0;µM). The calibration curve, which was based on the relationship between the peak current and the ofloxacin concentration, exhibited excellent linearity, with a correlation coefficient (<i>R</i>²) of 0.9854. Overall, the PGCN-modified glassy carbon electrode showed significant potential for the sensitive and selective detection of OFX.</p> Graphical Abstract <p></p>