DL-glutamic acid monohydrate crystal was synthesized from an aqueous solution by slow evaporation technique. The crystal was submitted to high-pressure regime (0.9-14.3 GPa) with intent to investigate its vibrational behavior and the occurrence of phase transitions. We performed Raman spectroscopy technique as probe and through the analysis of the Raman spectra we discovered three main structural phase transitions. The results showed that the first phase transition occurs around 0.9 GPa. In this phase transition, glutamic acid molecules suffer modifications in their conformations while water molecules are less affected. The second phase transition at 4.8 GPa involves conformational changes related to CO₂^-, NH₃⁺ units and the water molecules, while the third one, between 10.9 and 12.4 GPa, involved motions of several parts of the acid glutamic as well as the water molecules. Small changes in the lattice modes around 8.5 GPa precede the third transition. Considering the dynamic of high pressure, the second phase of DL-glutamic acid monohydrate crystal presented good stability compared with the second phase of its polymorphs αLGA and βLGA. In addition, water molecules seem play important role on this structural stability and all changes were reversible.