Abstarct: In the present study, a glassy carbon electrode was electrochemically modified with a poly(aniline)/poly(2-methoxyaniline-5-sulfonic acid) (PANI/PMAS) composite and applied for the simultaneous determination of paracetamol and tyrosine using differential pulse voltammetry in aqueous solutions. To characterize the surface of the PANI/PMAS-modified glassy carbon electrode, chronoamperometry, electrochemical impedance spectroscopy, field emission scanning electron microscopy (FE-SEM), and energy-dispersive X-ray spectroscopy (EDX) were employed. The PANI/PMAS-modified electrode exhibited superior performance compared to electrodes modified with PANI alone, PMAS alone, and bare glassy carbon. Various parameters, including pH, buffer type, buffer volume, aniline concentration, and PMAS concentration, were optimized using the one-variable-at-a-time method for the simultaneous determination of paracetamol and tyrosine. Under the optimized conditions, the electrode displayed a linear response for paracetamol and tyrosine in the concentration ranges of 0.1–30 μM and 0.1–20 μM, respectively, with limits of detection of 0.09 μM for paracetamol and 0.19 μM for tyrosine. Most coexisting pharmaceutical compounds did not interfere, indicating good selectivity of the electrode. Finally, the PANI/PMAS-modified electrode was successfully applied for the simultaneous determination of paracetamol and tyrosine in pharmaceutical tablets, human serum, and municipal water samples.