<p>MXene, an emerging class of two-dimensional nanomaterials with outstanding electrical conductivity and electrochemical properties, has attracted growing interest within the domain of flexible electronics. However, MXene flakes are difficult to spin independently due to the incomplete nanosheet alignment, interfacial void formation, and oxidative instability. The integration of MXene with other materials enables the development of novel MXene-based composite fibers that combine mechanical flexibility, electrical conductivity and multifunctional properties, thereby fulfilling the diverse requirements of flexible electronics. This review examines the recent developments in MXene-based composite fibers for flexible electronics. In this review, we initially present the principles and recent strategies for fabricating MXene-based composite fibers using synthetic polymers, natural polymers, and carbon-based nanomaterials. Next, the applications of MXene-based composite fibers are summarized, focusing on supercapacitors with enhanced electrochemical performance, sensors with high sensitivity, and electromagnetic shielding devices with exceptional absorption efficiency. Finally, the current challenges of MXene-based composite fibers are critically discussed, along with future directions emphasizing multifunctional integration, structure–property regulation, and sustainable production technologies.</p>