Single-layered MoS2 is a naturally stable material. Integrating spin, valley, and circularly polarized photons is an interesting endeavor to achieve advanced spin-valleytronics. In this study, room-temperature ferromagnetism in MoS2 induced by the magnetic proximity effect (MPE) of yttrium iron garnet (YIG) and the antiferromagnetic coupling at the interface is demonstrated. Insulating YIG without charge carriers is an excellent magnetic candidate featuring a long spin diffusion length and remarkable surface flatness, enabling long-range magnetic interactions with MoS2. Spin-resolved photoluminescence spectroscopy and magnetic circular dichroism (MCD) reveal that the spin-polarized valleys of MoS2 can achieve sustained ferromagnetism even at room temperature. The bandgap-sensitivity of MCD further demonstrates the extent of antiferromagnetic coupling between the MPE-induced moments of MoS2 and YIG. This work provides a layer-selected approach to study magnetic interactions/configurations in the YIG/MoS2 bilayer and highlights the role of MoS2 in achieving the MPE toward high temperature.