Because of the temperature-induced intervalley scattering, transition metal dichalcogenides (TMDCs) typically exhibit diminished valley polarization at room temperature, limiting their application in valleytronic devices. To address this issue, combining chiral perovskites with monolayer TMDCs provides a promising route for room-temperature valley polarization control. Here, the enhanced chiral-induced spin selectivity (CISS) effect in R -(+)- and S -(−)-α-methylbenzylamine (MBA)–based tin perovskites is substantially strengthened by introducing chiral seed layers. Leveraging spin-valley coupling, spin extraction at the chiral perovskite interface improves the valley polarization of monolayer tungsten disulfide (WS 2 ) to reach as high as 14.9% at room temperature. The enhanced CISS effect enables more efficient spin-selective charge transfer, thereby amplifying the carrier population imbalance between the K and K′ valleys in monolayer WS 2 . This asymmetry is further improved by the high-quality chiral perovskite substrates, which help suppress valley carrier recombination. Our study offers a promising approach by combining chiral seed–induced enhancement of the CISS effect in chiral perovskite with monolayer TMDCs to achieve excellent performance of valley manipulation.