Using mid-infrared data acquired by Moons and Jupiter Imaging Spectrometer (MAJIS) aboard the European Space Agency’s JUpiter ICy moons Explorer (JUICE) spacecraft during the 2024 lunar flyby, we retrieved lunar surface temperature and effective emissivity at high spatial and spectral resolution. By comparing three independent thermal-retrieval methods, we confirmed the main mare–highland contrasts and showed how roughness and observing geometry shape the infrared signal, providing a methodological test case for future MAJIS studies of Jupiter’s icy moons.