Ocean energy is an underutilized renewable energy source compared with hydropower and wind power. Therefore, the development of economical and efficient wave energy converters (WECs) is important and crucial for offshore power generation. The mooring tensioner is a critical device that can be used in point-absorber-type WECs, semisubmersible floats for oil and gas drilling, and floating wind turbines. A mooring tensioner is a system used to create, reduce, or maintain tension within the mooring lines by applying a force to the mooring line. Composite springs as mooring tensioners have several advantages compared to metal springs, such as corrosion resistance, high specific strain energy, appropriate fatigue performance, and the ability to flexibly adjust the spring constant without changing the overall dimensions. This paper reviews in detail the fatigue performance, seawater durability, and manufacturing methods of different composite materials as well as the current and potential applications of composites springs. In addition, recommendations for future research and opportunities for composite mooring tensioners are presented.