Abstract: Poly(vinylidenefluoride-co-trifluoroethylene) (P(VDF-TrFE)) is a copolymer of polyvinylidene fluoride (PVDF) that exhibits outstanding piezoelectric properties, mechanical properties, and biocompatibility. Therefore, the flexible piezoelectric sensors and energy harvesters based on P(VDF-TrFE) have a promising future in the fields of intelligent textiles, wearable electronic devices and medical and health systems. These devices can convert signals such as tactile, pressure, strain, acoustic waves or even physiological micro-vibrations into electrical signals or low-power electrical energy. This paper aims to provide an in-depth analysis of the mechanism of P(VDF-TrFE) piezoelectric properties, summarize various strategies to enhance the piezoelectricity of electrostatically spun P(VDF-TrFE) nanofibers, and provide a comprehensive overview of the applications of P(VDF-TrFE)-based flexible piezoelectric sensing and energy harvesting. Specifically, research advances in the areas of pressure and tactile sensing, acoustic sensing, biological tissue sensing, physiological micro-vibration sensing, and energy harvesting are summarized. Finally, the emerging application scenarios of electrospun piezoelectric polymer nanofibers are illustrated, the current challenges and future prospects in this field are discussed.