Nanofiber-based piezoelectric energy generators could be scalable power sources applicable to various electrical devices and systems by scavenging mechanical energy from the environment. This chapter highlights recent advances in nanofiber nanogenerators, discusses their working principles, and addresses performance issues including piezoelectricity, energy conversion efficiencies, and possible false artifacts during experiments. Among many energy harvesting platforms, piezoelectric nanogenerators made of PVDF (polyvinylidene fluoride) and fabricated by means of electrospinning processes such as conventional, modified and near-field electrospinning (NFES) are the key focus of this chapter. Material and structural analyses on fabricated nanofibers using tools such as XRD (X-ray diffraction), FTIR (Fourier transform infrared), SHG (second harmonic generation) and PFM (piezoresponse force microscopy) and Raman spectroscopy toward the characterizations of piezoelectric nanofibers are also presented. The potential applications using fiber-based nanogenerators include flexible and wearable electronics.