Abstarct: Applications of nanomaterials such as multi-walled carbon nanotubes (MWCNTs) and gold nanoparticles, electrochemical mediators such as methylthoiuracil and poly alizarin red S were investigated for modifying the surface of glassy carbon and carbon paste electrodes for fabrication of electrochemical sensors for the determination of drug compounds such as verapamil, gemfibrozil and dopamine. In this regard, the glassy carbon electrode was modified with multi-walled carbon nanotubes (MWCNT/GCE) and electrochemical oxidation and voltammetric determination of verapamil were studied at the surface of this modified electrode. The results revealed that oxidation of the mentioned compound at the surface of unmodified electrode exhibits an ill-defined oxidation peak; while at the surface of the modified electrode a sharp peak with significant current was observed. The linear calibration ranges of the method for determination of verapamil using cyclic and differential pulse voltammetry were 2.50-70.00 µmol L-1; while the detection limits baxsed on these methods were and 2.00 µmol L-1 and 1.60 µmol L-1, respectively. The modified electrode as an electrochemical sensor has the capability for the determination of the verapamil in the pharmaceutical samples and also in the biological samples like human serum. The carbon paste electrode was modified with methylthiouracil and was used for the determination of dopamine using voltammetric methods. Due to the presence of nucleophile agent as the modifier in the bulk of carbon paste electrode, the prepared electrochemical sensor shows high electrocatalytic activity towards the oxidation of dopamine through 1,4 Michael addition reaction. The electrochemical behavior of dopamine at the surface of methylthiouracil modified carbon paste electrode was studied using cyclic voltammetry and chronocoulometry. The more effective variables on the sensitivity of the electrode were screened by Plackett–Burman design and subsequently optimized using central composite design. Under the optimum conditions a linear calibration graph over the range of 0.20-15.00 µmol L-1 with a detection limit of 73.00 nmol L-1 was obtained using adsorptive stripping differential pulse voltammetry. The conducted studies confirmed the ability of the proposed sensor for dopamine determination in the pharmaceutical samples. The glassy carbon electrode surface was modified with multi-walled carbon nanotubes. Afterward, gold nanoparticles were electrochemically immobilized at the MWCNT/GCE. Scanning electron microscopy (SEM), energy dispersive x-ray (EDX) and electrochemical impedance spectroscopy (EIS) were used for characterization of the MWCNT/Au modified glassy carbon electrode (MWCNT/Au/GCE) surface. Determination of gemfibrozil was studied by adsorptive stripping square wave voltammetry as well as impedimetry. The linear calibration ranges for determination of gemfibrozil were 0.15-45.00 µmol L-1 and 0.10-45.00 µmol L-1, respectively; while detection limits of voltammetry technique was 0.10 µmol L-1 and for impedimetry it was 74.00 nmol L-1, respectively. Finally, gemfibrozil determination in the pharmaceutical and biological samples was assessed at the surface of the proposed modified electrode. An electrochemical sensor baxsed on deposition of polymeric film by using electrochemical method on the surface of glassy carbon electrode was fabricated for determination of gemfibrozil using differential pulse voltammetry. For this purpose, Alizarin red S which is a dye was used in order to increase the dispersion ability of MWCNT in aqueous medium and this phenomenon took place by non-covalent interactions between the dye and MWCNT. The resulting composite was then electropolymerized at the surface of GCE by cyclic voltmaatery method. Then the fabricated electrode was used for determination of gemfibrozil using differential pulse voltammetry technique and the linear concentration range and detection limit for the determination of this analyte at the surface of poly alizarin red S/MWCNT were 1.00-22.00 µmol L-1 and 0.24 µmol L-1, respectively. In addition, determination of the gemfibrozil was evaluated in real samples of human blood serum, water and capsules with differential pulse voltammetry.