Abstract Herein, high‐performance flexible and stable Cu‐Ni nanoalloy decorated carbon nanotube (CNT) reinforced poly(vinylidene fluoride) (PVDF) based piezoelectric nanogenerator is presented for the first time with very high current and power density. The formation of crystalline β‐phase is confirmed using FT‐IR and Raman spectra analysis. HR‐TEM study reveals the formation of Cu‐Ni nanoalloys with well‐defined interconnected structure with CNT. The Cu‐Ni nanoalloy decorated CNT‐PVDF nanogenerator device exhibits a high output voltage of 12 V and high current density of 0.3 µ A cm −2 compared to pristine PVDF nanogenerator (4 V and 10 nA cm −2 ). Very high power density of 204 µ W cm −3 is obtained from the nanocomposite nanogenerator. Piezoelectric force microscopy study reveals very high piezoelectric charge coefficient ( d 33 ) of about 160 pm V −1 from Cu‐Ni decorated CNT‐PVDF. Very stable output performance with almost no degradation till 1500 cycles is observed from the Cu‐Ni nanoalloy CNT‐PVDF nanogenerator. Such high stability is due to its dramatic improved high tensile strength of 60 MPa. Very high dielectric constant of 500 is observed from Cu‐Ni decorated CNT‐PVDF as compared to pristine PVDF ( ε ’ ≈ 20). The dramatic increase in output performance even under without electrical poling is discussed in light of self‐dipole alignment, in‐situ poling, high d 33 , interfacial polarization, and enhanced dielectric properties.