MXenes are emerging 2D materials with intriguing properties such as excellent stability and high conductivity. Here, a systematic study on the Raman spectra of 2D α‐Mo2C (molybdenum carbide), a promising member in MXene family, is conducted. Six experimentally observed Raman modes from ultrathin α‐Mo2C crystal are first assigned with the assistance of phonon dispersion calculated from density functional theory. Angle‐resolved polarized Raman spectroscopy indicates the anisotropy of α‐Mo2C in the b–c plane. Raman spectroscopy is further used to study the unique domain structures of 2D α‐Mo2C crystals grown by chemical vapor deposition. A Raman mapping investigation suggests that most of the α‐Mo2C flakes contain multiple domains and the c‐axes of neighboring domains tend to form a 60° or 120° angle, due to the weak MoC bonds in this interstitial carbide and the low formation energy of the carbon chains along three equivalent directions. This study demonstrates that polarized Raman spectroscopy is a powerful and effective way to characterize the domain structures in α‐Mo2C, which will facilitate the further exploration of the domain‐structure‐related properties and potential applications of α‐Mo2C. The Raman spectra of 2D α‐Mo2C (molybdenum carbide) crystal is systematically studied. Six experimentally observed Raman modes of 2D α‐Mo2C are assigned for the first time. Angleresolved polarized Raman spectroscopy indicates the in‐plane anisotropy of α‐Mo2C. Raman mapping reveals the unique domain structures of α‐Mo2C flakes grown by chemical vapor deposition.