A hybrid nanogenerator (HNG) offers both high output performance and flexibility by utilizing the synergy between piezoelectric and triboelectric mechanisms. Achieving high output performance, reproducibility, and mechanical stability in a HNG device is still a major challenge. Here, we demonstrate the design and fabrication of a flexible HNG device based on the composite of a lead-free piezoelectric ceramic and the triboelectric polymer poly(dimethylsiloxane) (PDMS). The piezoelectric ceramic oxide (Bi0.785K0.035Ba0.180)(Fe0.750Ti0250)O3 (BKBFT/MPB-piezo) exhibits improved piezoelectric properties at the morphotropic phase boundary (MPB) in the BiFeO3-Bi0.5K0.5TiO3-BaTiO3 ternary phase diagram. We find that the composite 90 wt % PDMS-10 wt % MPB-piezo offers optimum device performance and flexibility. Interestingly, the incorporation of multiwalled carbon nanotubes (MWCNTs), a conducting filler, significantly enhances the device’s performance without the aid of electric field poling. MWCNTs form nanoelectrical bridges that aid in charge transfer and improve the composite’s structural homogeneity. The 89 wt % PDMS-10 wt % MPB-piezo-1 wt % MWCNT composite displays a peak-to-peak open-circuit voltage (Vpp), short-circuit current (Isc), and power density (U) of 22 V, 1.8 μA, and 72 nW/cm2, respectively. Furthermore, we show the capability of the composite to be used as a wearable human pulse sensor.