In this work, electrospun MXene (Ti3C2Tx) functionalized Polyvinylidene fluoride (PVDF) composite nanofiber is firstly proposed as a promising negative triboelectric layer for boosting triboelectric energy harvesting performance. The Ti3C2Tx nanosheets are blended into the PVDF matrix followed by a standard electrospinning process to improve the dielectric property and surface charge density of the nanofiber that substantially improves the triboelectric performance. The dielectric modulation of PVDF nanofibers by incorporating conductive MXene nanosheets significantly enhanced the dielectric constant and the surface charge density of nanofiber by 270% and 80%, respectively. The Triboelectric nanogenerator (TENG) based on PVDF/MXene composite (PMC) nanofiber and Nylon 6/6 nanofiber is fabricated that can deliver a peak power of 4.6 mW (power density:11.213 Wm−2) at the matching load of 2 MΩ, which is 1.58 times higher than that of pristine PVDF nanofiber fabricated in this study. As-fabricated TENG shows excellent performance under low-frequency impact motions with highly stable (> 60 K cycles) output signals, quickly charges the storage capacitors, and sustainably operates the low power electronics and commercial LEDs. In addition to energy harvesting, the TENG is successfully demonstrated as a self-powered foot motion sensor, that can automatically control the step lights based on the human foot motion over the stair.