In this study, electropolymerization of glycine (Gly) was carried out to enhance the sensitivity of the carbon paste electrode (CPE) blended with multi-walled carbon nanotubes (MWCNTs) for electroanalysis of diclofenac (DCF). Analytical applications and electrochemical performance were examined using various voltammetric methods, including differential pulse voltammetry and cyclic voltammetry. Atomic force, scanning electron microscopy, dispersive X-ray, X-ray diffraction, and Raman spectroscopy were used to ascertain the surface topology of the modifier. The modified sensor with high electrocatalytic properties could electrochemically oxidize DCF, resulting in an enhanced current compared to the bare CPE when an anodic peak was detected at 0.77 V peak potential for the bare CPE, consisting of 0.1 mM DCF and 2.11 µA peaks current. The working electrode CPE was then modified with MWCNT and glycine. For MWCNT/CPE, a peak was seen at 5.20 µA and 0.75 V, and a more intense peak was observed for poly(Gly)-MWCNT/CPE at 11.52 µA and 0.74 V. The poly(Gly)-MWCNT/CPE exhibited a five-fold enhancement of peak current compared to bare CPE. The modified electrode displayed fast electron transfer, reproducibility, and repeatability. The study explored how factors like immersion time, pH variation, scan speed, and substance concentration could influence the peak current of DCF. Methods such as differential pulse voltammetry and cyclic voltammetry were utilized to examine the electrochemical oxidation behavior of DCF. The concentration variation is 0.5 µM to 7.0 µM, and the detection limit was 7.96 × 10-8 M. The rate constant (ks) for the electrochemical process was 1.710 s-1. The DCF of pharmacological and biological test substances was measured using the constructed modified electrode.