Haloperidol, with molecular formula C21H23ClFNO2, is a conventional antipsychotic drug used to relieve the symptoms of schizophrenia. Although its pharmacology has been extensively reported, only few studies focused on its vibrational features. In this work, Raman spectroscopy was used to investigate the vibrational properties of the haloperidol crystal under high-pressure conditions up to approximately 5.9 GPa. Our results showed changes in the low wavenumber bands accompanied by some changes in the internal vibrational modes, indicating the occurrence of a phase transition. Analysis of the Raman spectra shows phase transitions around 2.0 GPa and 4.2 GPa, with the disappearance and appearance of some modes in addition to discontinuities in the evolution of the frequencies of several normal modes of vibration. Such changes involved modes located in the region of external modes while others involved modes of the molecular skeleton and modes that participate in hydrogen bonds. At 4.2 GPa the changes were related to small conformational changes associated with hydrogen bonds and small deformations in the haloperidol molecules. At 2.0 GPa it was observed a change corresponding to the lattice modes, indicating a structural phase transition with conformational change.