Excellent piezoelectric properties of d33* = 768 pm/V and strain = 0.07% at 1 kV/mm, were obtained by lead-free in (Na0.52K0.4425Li0.0375)(Nb0.86Ta0.06Sb0.08)O3 ceramics. They displayed good temperature stability up to 200°C. Significantly enhanced piezoelectricity originated from nanodomains of width 20–30 nm, and the result was confirmed by transmission electron microscopy. The above-mentioned nanodomains emerged because of low domain wall energy near polymorphic phase transition regions and insignificant differences in cell parameters between orthorhombic and tetragonal phases. The nanodomain configuration easily responded to an external electric field, leading to high electric field-induced strain.