This study explores the decoupling of carrier-phonon transport in perovskite thermoelectrics through entropy engineering. By introducing high entropy at the A-site, the lattice thermal conductivity of SrTiO3-based perovskite thermoelectrics is significantly reduced to the amorphous limit of 1.25 W m−1 K−1. Simultaneously, the Ti displacement is tuned, improving the weighted mobility to 65 cm2 V−1 s−1. This carrier-phonon decoupling leads to a significantly enhanced μW/kL of -5.2 × 103 cm3 K J−1 V−1. The maximum zT of 0.24 at 488 K and an estimated zT of -0.8 at 1173 K in (Sr0.8Ba0.2Ca0.2Pb0.1La0.2)TiO3 film are among the best reported for n-type thermoelectric oxides. The results demonstrate that entropy engineering is a promising strategy to decouple carrier-phonon transport and achieve higher zT in thermoelectrics.This study explores the decoupling of carrier-phonon transport in perovskite thermoelectrics through entropy engineering. By introducing high entropy at the A-site, the lattice thermal conductivity of SrTiO3-based perovskite thermoelectrics is significantly reduced to the amorphous limit of 1.25 W m−1 K−1. Simultaneously, the Ti displacement is tuned, improving the weighted mobility to 65 cm2 V−1 s−1. This carrier-phonon decoupling leads to a significantly enhanced μW/kL of -5.2 × 103 cm3 K J−1 V−1. The maximum zT of 0.24 at 488 K and an estimated zT of -0.8 at 1173 K in (Sr0.8Ba0.2Ca0.2Pb0.1La0.2)TiO3 film are among the best reported for n-type thermoelectric oxides. The results demonstrate that entropy engineering is a promising strategy to decouple carrier-phonon transport and achieve higher zT in thermoelectrics.