When designing helical gears, the goal is to optimize gear weight, efficiency, and noise while simultaneously achieving the required strength. In this study, the macro geometry of a helical gear pair was optimized for low weight, high efficiency, and low noise; further, trends of optimal solutions for five combinations of the three objectives were analyzed. The gear mass and efficiency were directly used as the design objectives. However, since the calculation of the gear noise is generally very complicated and time-consuming, the gear noise has not been directly used as the design objective, and the peak-to-peak static transmission error (PPSTE), which is the main source of the gear vibration, was selected as the design objective for the gear noise in the optimization. The objectives exhibited a trade-off relation between each other in the optimal space. If one of them was omitted, the objective considerably deteriorated. To analyze the results, the objectives were normalized and scored. As a result, most of the top ranks were from the optimal solutions considering the mass, efficiency, and PPSTE. Therefore, all three objectives should be considered in the gear optimization for low weight, high efficiency, and low noise.