Owing to their strong nonlinearity, cadmium sulfide (CdS) nanostructures are promising platforms for investigating the fundamental physics of light–matter interactions. However, observing the strong exciton–photon interactions in CdS microstructures at room temperature continues to present significant challenges, primarily because of the limited exciton binding energy. This study reports the direct observation of the interaction between excitons and microcavity photons in Sn-doped CdS microsheets without extreme fabrication conditions. Using angle-resolved photoluminescence (ARPL) spectroscopy, Rabi splitting of polaritons up to 163 meV was obtained at room temperature. Additionally, the temporal lasing dynamics of the Sn-doped CdS microsheets were investigated using a streak camera system. Most importantly, exciton–polariton condensation and coherent exciton–polariton lasing in the Sn-doped CdS microsheet was observed at room temperature. These results advance the fundamental understanding of exciton–polaritons in Sn-doped CdS microsheets and their applications in miniaturized microlaser devices.