With the widespread use of wearable electronics, portable and flexible energy harvesting devices with a high sensitivity have attracted considerable interest. Herein, an ultrasensitive piezoelectric nanogenerator (PNG) made of a few layers of 2D-MoS2-incorporated electrospun poly(vinlydine fluoride) (PVDF) nanofiber webs (NFW) is described for the first time. As a result of the semiconducting properties and piezoelectric functionalities of 2D-MoS2, the resultant piezoelectric performance of PNG can be modulated, which leads to a material suitable for wearable electronics to power devices and to fabricate self-powered biomedical nanosensors for diagnosis, such as heartbeat monitoring, pressure mapping from footsteps, and speech signal abnormality. We have demonstrated that our PNG has a 70 times improvement in acoustic sensitivity than nanosensors made of neat PVDF NFW and are able to charge a capacitor quickly (e.g., 9V is charged within 44s). As a result of the ultrafast charging performance and external low-impact detection capability of 2D-MoS2-modulated PNG, this paves the way to design cost-effective self-powered wearable electronics and robotics.