The solubility and supersolubility of L-phenylalanine in aqueous solutions is firstly reported in this work. At temperatures from 273.15 to 343.15 K, both solubility and supersolubility in water generally increase with the temperature, and the average metastable zone width is about 8.3 degrees C. At the temperature of 298.15 K, the solubility remarkably decreases with an increase in the concentration of ethanol, which indicates that ethanol can be used as an antisolvent for the precipitation and crystallization of L-phenylalanine. When sodium chloride is added to the solution, the solubility of L-phenylalanine increases with the concentration of sodium chloride.