Abstract In recent years, flexible sensor devices have demonstrated significant potential for applications in basic science, healthcare, and health monitoring. Fiber–based sensing devices have garnered considerable attention due to their high performance, wearing comfort, potential for mass production, and broad range of applications. Material and structure are the two primary factors that influence the performance of fiber sensor devices. This review systematically summarizes the recent progress in research on flexible sensor devices based on conductive fibers. First, the classification of sensing materials and their sensing mechanisms is briefly introduced. Subsequently, the structural types of conductive fibers and their corresponding preparation methods are comprehensively discussed. Furthermore, the emerging applications of conductive fibers in flexible wearable electronics, medical fields, and multifunctional applications are explored. Finally, potential challenges and future prospects for conductive fiber–based flexible sensing devices are discussed.