Ni–YSZ cermet was exposed to hydrogen containing different concentrations of H2S to identify the phases formed under various conditions using Raman spectroscopy and X-ray diffraction (XRD). For Ni–YSZ samples exposed to hydrogen containing 100ppm H2S at 727°C for 5 days, thermodynamic calculations indicate that Ni–YSZ would be stable and XRD analysis was unable to detect any changes. However, the vibration modes of Ni3S2 were detected using Raman spectroscopy, suggesting that Raman spectroscopy could be a powerful tool for in situ study of sulfur poisoning of SOFC anodes. For Ni–YSZ cermet exposed to hydrogen containing 10% H2S at 950°C for 5 days, Ni was converted to nickel sulfide, and vibration modes of NiS were detected using Raman spectroscopy.