Raman spectroscopy was used to analyze mixtures of urea and water in order to identify the influence of the urea concentration on the solution's freezing point. Our approach consisted in the analysis of urea aqueous solutions and the determination of their phase transitions at low temperatures. Hence, Raman spectra of these solutions were acquired in a -30 to 10 °C temperature range. This enabled us to build the experimental phase diagram of the urea-water binary system.