Recently, industrial world has been directed to environmental awareness, specially machine manufacturing technologies which are considered as a source of environmental contamination. A serious step toward reducing the adverse impact to the environment was taken when designing and manufacturing mechanical elements such as gears. Years ago, designers used conventional mechanical design of gears, either metallic or polymer aiming at decreasing product cost, operating cycles and increasing gear quality. This approach is lacking the interests of environmental aspects, leading to the concept of sustainable design and manufacturing. The magic word of sustainability is considering the environmental aspects as well as economy and society. The need for sustainable design and manufacturing of gears made the researchers and designers use new technologies in metallic gears including implementing sustainable design methods of recyclability of metal waste. Although the efforts made to sustain metallic gears, the amount of waste to be recycled could be costly expensive. In this manner, the direction to wisely apply the bio-based or biodegradable materials in the design and manufacture of gears has achieved the target of sustainability. This paper gives an overview of the latest techniques in metal and plastic gears manufacturing with a comparison between them favoring the usage of polymer materials to fully complete the main aspects of sustainability. Real design examples of plastic gears are presented with different design inputs and gears materials. Design procedure of plastic gears presented promotes the investigation of plastic gears performance, selection of different plastic gears materials and development of computer-aided design methodology.