Gears are crucial elements in mechanical systems and contribute to the overall performance of machinery. As such, optimization of gearbox transmission systems remains a challenging problem faced by researchers and designers for numerous years. In the present work, three objectives viz volume, power output and centre-distance are investigated simultaneously. A two-stage spur gearbox design problem is formulated with eight design variables viz. face-width (stage 1), face-width (stage 2), shaft diameter (stage1), shaft diameter (stage 2), module, pinion teeth number( stage 1) and pinion teeth number (stage 2) considered.Two geometric and three design constraints are formulated. Pareto frontiers are generated using NSGA-II evolutionary algorithm. The Pareto frontier is investigated using decision tools viz. FUZZY, LINMAP and TOPSIS and the best solutions selected using the deviation index. Validation of results was done using previous reports in literature and geometric modelling software. Variation and sensitivity studies indicate that module, pinion tooth number and face-width variables had a higher influence on volume as compared to power output and centre-distance. The combined optimization of volume, centre-distance and power output reveals key insights for the design of compact gearboxes.