This work presents the utilization of an MCDM technique to address the Multi-Objective Optimization Problem (MOOP) associated with a two-stage helical gearbox with second-stage double gear-sets. The objective is to identify the optimal key design variables that will enhance gearbox efficiency and minimize gearbox dimensions. Additionally, the analysis focused on three crucial design parameters: the gear ratio of the first stage, and the coefficients of wheel face width (CWFW) for both the first and second stages. In addition, the Measurement of Alternatives and Ranking according to COmpromise solution (MARCOS) methodology was selected to address the challenge of multi-objective optimization in tackling Multi-Criteria Decision Making (MCDM) problems. Furthermore, the MEREC approach was chosen to compute the weight criterion. The study’s findings assist in defining the optimal values for three critical design parameters in the development of a two-stage helical gearbox with second-stage double gear sets.