© 2020 The Society of Fiber Science and Technology, Japan. Carbon nanotube (CNT) yarn drawn from CNT arrays has recently attracted considerable interest for various applications in wiring harnesses, composites, smart textiles, and high strength structural materials. Although the excellent properties and functions of CNTs are expressed at nanometer scale, it is quite difficult to maintain these nanoscale properties while upscaling to bulk CNT spun yarn. This paper aims to provide an overview of the rapid synthesis of spinnable tall and dense CNT arrays, the processing and improvement of the physical properties of CNT spun yarn, and the application of CNT spun yarn in the fields of energy and mechanical devices.