The low surface charge density and consequent unsatisfactory energy conversion efficiency of nanogenerators hinder their capacious utility toward the emerging field of wearable electronics. The strategy of introducing dielectric fillers into a polymer matrix attempts to improve dielectric constant and, thereby, to enhance surface charge density but can hardly yield sufficient energy conversion efficiency. Herein, we report a high performance flexible and compressible triboelectric nanogenerator (FC-TENG) based on a lead-free dielectric material, potassium sodium niobate (KNN), embedded with Ti3C2Tx MXene fillers, blended into poly-vinyl alcohol (PVA) using an electrospinning technique. The role of MXene in dielectric functionalization is to promote the interfacial polarization effect by forming micro-capacitor structures or percolation systems and, thereby, to endow high charge-inducing and charge-trapping capabilities. As a result, the prepared 4 vol. % MXene loaded KNN/PVA nanofibers achieve a higher dielectric constant/dielectric loss factor, which leads to enhanced energy conversion efficiency of FC-TENGs with a maximum power density of ∼2780 mW/cm2. In addition, the selected device was employed into shoe-insoles to demonstrate its ability of capturing biomechanical energy, which reveals its potential to be utilized as a wearable power-source for next generation devices.