Rare-earth elements-doped lead-free piezoelectric ceramics are a valuable multifunctional material. The Er3+-doped (Ba, Ca) (Ti, Sn)O-3 (BCTS-Er) ceramics with various polymorphic phase transition (PPT) were synthesized through a traditional solid-state reaction route. The component with a coexisting phase structure of orthorhombic and tetragonal is abbreviated as BCTS-Er-I, and the component with a coexisting phase structure of rhombohedral and tetragonal is abbreviated as BCTS-Er-II. The BCTS-Er ceramic exhibits high piezoelectric properties (BCTS-Er-I: d(33) = 260 pC/N; BCTS-Er-II: d(33) = 310 pC/N) and strong green photoluminescence (PL) emission. The effects of polarization on the PL properties of the BCTS-Er ceramics with various PPT were systematically studied. Compared with the PL intensity of the unpoled sample, that of the poled BCTS-Er-I ceramics weakened by 70%, while that of the poled BCTS-Er-II ceramics increased by four times under the electric field at 10 kV/cm. The effect of polarization treatment on the PL properties of the BCTS-Er ceramics is attributed to the polarization-induced phase transition, lattice distortion, the symmetry of the host lattice, and domain reorientation.