It is known that in the development of electrochemical immunosensors, the electrode is used both for the immobilization of antibodies and for carrying out the redox reaction. Therefore, it is important to have an electrical conductive surface with the possibility of retaining the antibodies. To achieve a better sensitivity and a greater work concentration range, the surface of the electrode can be modified with different appropriate materials such as multi-walled carbon nanotubes (MWCNT) and gold nanoparticles (AuNPs) among others. In this work, the design of a platform for an electrochemical immunosensor was studied. Thus, the optimization of screen printed carbon electrodes modified with a dispersion of MWCNT in polyethylenimine (MWCNT/PEI) and AuNPs was performed, through a multivariate optimization and experimental design. A factorial design of 3(2) levels was used, where the variables were the volumes of AuNPs solution and MWCNT/PEI dispersion for given concentrations, respectively. The optimized responses were the cathodic peak current for the reduction of K-3[Fe(CN)(6)] and the charge transfer resistance for the K-4[Fe(CN)(6)]/K-3[Fe(CN)(6)] redox couple, using cyclic voltammetry and electrochemical impedance spectroscopy. The cathodic peak current was fitted using a lineal model, while the charge transfer resistance was fitted by a quadratic model. The desirability function was used to determine the surface with a lower resistance to charge transfer and a higher current for the reduction of K-3[Fe(CN)(6)]. Therefore, the optimized nanostructured surface promises to be a suitable structure for the development of a new electrochemical immunosensor.