Er³⁺-doped SrBi₄Ti₄O₁₅–Bi₄Ti₃O₁₂ (SBT–BIT–xEr³⁺, x = 0.00, 0.05, 0.10, 0.15 and 0.20) inter-growth ceramics were synthesized by the solid-state reaction method. Structural, electrical and up-conversion properties of SBT–BIT–xEr³⁺ were investigated. All samples showed a single phase of the orthorhombic structure. Raman spectroscopy indicated that the Er³⁺ substitution for Bi³⁺ at A sites of the pseudo-perovskite layer increases the lattice distortion of SBT–BIT–xEr³⁺ ceramics. The substitution of Bi³⁺ by Er³⁺ leads to a decrease of dielectric loss tanδ and an increase of conductivity activation energy. Piezoelectric constant d₃₃ was slightly improved, but dielectric constant was decreased with the Er³⁺ doping. The SBT–BIT–xEr³⁺ ceramic with x = 0.15 exhibits the optimized electrical behavior (d₃₃ ~17 pC/N, tanδ ~0.83%). Moreover, two bright green (532 and 548 nm) and one red (670 nm) emission bands were observed under the 980 nm excitation. Optimized emission intensity was also obtained when x = 0.15 for the SBT–BIT–xEr³⁺ ceramic. Therefore, this kind of ceramics ought to be promising candidates for multifunctional optoelectronic applications.