The following study describes the electropolymerization of phenothiazine methylene blue (MB) monomer on conductive 3D printer laments made of polylactic acid doped carbon black (PLA-CB). Poly(methylene blue) (PMB) thin layers were successfully synthesized on PLA-CB electrodes using various electrochemical techniques, including cyclic voltammetry (CV), chronopotentiometry (CP), and chronoamperometry (CA). The threshold values required to initiate the polymerization process were found to be 470 mV and 10 µA.cm 2 for the potentiostatic and galvanostatic modes respectively. Afterward, microscopic and spectroscopic characterization by SEM, Raman, as well as, XPS con rmed the successful modi cation of the PLA-CB surface with a thin layer of saccharin counter ions-doped PMB.The modi ed electrode PMB/PLA-CB was then tested for its ability as an electrochemical sensor for uric acid. The analysis conducted by cyclic voltammetry and differential pulse voltammetry (DPV) demonstrated a faster rate for electron transfer, consequently, uric acid can be electrochemically oxidized at a high number of active sites. The modi ed conductive 3D printer lament tested in the present study can be considered a promising sensor, not only for uric acid but also for other analytes contained in pharmaceuticals and biological samples.