A modified glassy carbon electrode with carbon black (CB) and gold nanoparticles (AuNPs) within a crosslinked chitosan (CTS) film is proposed in this work. The electroanalytical performance of the modified CB-CTS-AuNPs/GCE has been evaluated towards the voltammetric sensing of ketoconazole (KTO), a widespread antifungal drug. The nanocomposite was characterized by scanning electron microscopy, X-ray diffraction spectroscopy, and electrochemistry experiments. The evaluation of the electrochemical behaviour of KTO on the proposed modified electrode shows an irreversible oxidation process at a potential of +0.65 V (vs. Ag/AgCl (3.0 mol L-1 KCl)). This redox process was explored to carry out KTO sensing using square-wave voltammetry. The analytical curve was linear in the KTO concentration range from 0.10 to 2.9 μmol L-1, with a limit of detection (LOD) of 4.4 nmol L-1 and a sensitivity of 3.6 μA L μmol-1. This modified electrode was successfully applied to the determination of KTO in pharmaceutical formulations and biological fluid samples.