The advent of the Internet of Things (IoT) has triggered extensive demand for electronic devices with various form factors, such as wearable electronic devices. In particular, electronic textiles, which integrate electronic functions into human-friendly fabrics, have been studied at both the fiber and fabric level. Because the utilization of wearable electronic devices such as sensors, displays, and so on is basically limited by the energy capacity of the wearable devices, developing highly efficient power generating and storage devices in wearable forms has been considered very important at a power consumption point of view. Likewise, switching devices are also required to cut off electric power to unused electronic parts for efficient power management. However, the high leakage current in the switching devices reported has so far precluded the practical use of wearable applications. In this work, we demonstrate fiber-based TFTs with an Al2O3-MgO nanolaminate layer as gate insulator. The developed fiber-based TFTs exhibited an excellent on/off ratio over 108 and good mobility of over 3 cm(2)/(V s). From a power consumption point of view, more importantly, the fiber-based TFTs showed leakage and off current of less than 10(-9) and 10(-13) A, respectively, which is the lowest value ever in fiber-based TFTs so far and as low as the flat devices. These results are of great importance for validating their practical use especially in wearable electronics where wearable devices generally possess their limited battery capacity. In addition, the low-temperature vacuum deposition method used in this work also allows the fiber-based TFTs to be produced in the same manner as conventional flat TFTs.