The addition of ZnO nanowhiskers (ZnOw) in lead zirconate titanate (PZT) matrices results in reinforced composite materials but deteriorates their electrical properties. In this study, novel piezoelectric PZT/ZnOw composites modified with Nb2O5 were successfully fabricated using solid-state sintering method. The experimental results showed that the addition of 0.5 wt% Nb2O5 resulted in highly dense and homogenous PZT composites after sintering at 1150°C, with good piezoelectric and ferroelectric properties similar to pure PZT, specifically piezoelectric constant d33=665 pC/N, electromechanical coupling factor kp=0.7, relative dielectric constant ɛ=5048, and remnant polarization Pr=30.2 μC/cm2. The “soft effect” of Nb5+ ions, reflected in the improvement of the aforementioned properties, is attributed to the accommodation of Nb5+ ions at the B sites of the lattice of PZT. Compared with the PZT/ZnOw reinforced composites, the mechanical properties were slightly improved by adding 0.5 wt% Nb2O5, where flexural strength σf of 128 MPa and fracture toughness KIC of 1.46 MPa·m1/2 were measured.