This study compares the sensing performance of glassy carbon electrodes (GCE) modified with graphene (GR), multiwalled carbon nanotubes (MWCNTs), and graphene-multiwalled carbon nanotube (GR-MWCNT) composites for the simultaneous detection of ascorbic acid (AA), dopamine (DA), and uric acid (UA). Among these electrodes, GR-MWCNT/GCE exhibited the highest sensitivity and the lowest detection limit. Using differential pulse voltammetry (DPV), AA, DA, and UA can be simultaneously detected at low potentials of -0.032, 0.206, and 0.34 V vs Ag/AgCl, with sensitivities of 0.076, 1.38, and 0.181 μA μM