This paper describes the decoration of pencil graphite electrode (PGE) with a thin film of solochrome black T (SBT) and N-doped carbon nanodots (N-CNDs)/ cobalt nanoparticles (CoNPs) to amplify signal of the measurement. This nanocomposite was chosen to enhance surface activity and electron transfer toward donepezil HCl (DZ HCl) oxidation. The physical properties of nanocomposite were characterized by scanning electron microscope (SEM), Fourier transform infrared spectroscopy (FTIR), electron impedance spectroscopy (ESI) and energy dispersive X-ray (EDX) spectroscopy. Cyclic voltammetry was utilized to quantify DZ HCl at the modified PGE in Britton-Robinson buffer (pH = 6.5). Under optimized experimental conditions, peak current increased with the increase in the concentration of DZ HCl and was linear between the range of 1.5 nM–400 μM with a relatively low detection limit of 0.0005 μM. Due to high sensitivity, simplicity and cost-effectiveness of the designated sensor; it was used as a simple method for detecting DZ HCl in rabbit plasma and during its pharmacokinetic study.