By impressive mechanical properties, strong and lightweight carbon nanotube yarns and fibers have been reported. Among the mechanical properties of yarn, toughness is considered an important mechanical property for the protection of damage caused by external force. Here, by bio-mimicking the human muscle structure, dramatically increased toughness of carbon nanotube yarn is reported. The bio-inspired tough carbon nanotube (CNT) yarn, which is simultaneously increased in strength and elongation, is made by poly(vinyl) alcohol (PVA) infiltration and coiled multi-strand structure. This bio-inspired tough yarn provides a high-energy absorption (357.2 J/g), which is higher than spider dragline silk (165 J/g), Kevlar (78 J/g), and previous spinnable carbon nanotube yarns. Also, not only demonstrates high tough performance in various conditions such as water and temperature but also shows an ease in shape change by using water. This sewable, wearable, and shape controllable tough yarn has a potential for various applications such as bulletproof material, wearable device, stretchable electrode, aerospace industry, and artificial muscle.