Using a laser monitoring observation technique, the solubilities of 1-ethylpyridinium hexafluorophosphate in ethanol + water binary solvent mixtures have been measured from (278.15 to 345.15) K. The experimental data were well correlated with the modified Apelblat equation. The solubility of l-ethylpyridinium hexafluorophosphate in ethanol + water is higher than that in water and ethanol, respectively, and reaches the maximum value when the mass fraction (w) of water in the ethanol + water binary solvent mixtures is equal to 0.40.