Refractive indices and densities of the 2-propanol + water + 1-butyl-3-methylimidazolium tetrafluoroborate ([bmim][BF4]) ternary system have been measured at 298.15 K. Physical properties of 2-propanol + water and water + [bmim][BF4] binary mixtures have also been measured at the same temperature, whereas the 2-propanol + [bmim][BF4] mixture has been measured at 323.15 K, because the total miscibility for this mixture is achieved above this temperature. Molar volume and excess properties have been calculated from the experimental data to analyze the behavior of the mixtures. The refractive index has been correctly adjusted to a third-order polynomial expansion model, whereas density has been adjusted to a second-order equation. Excess molar volumes and refractive index deviations have been successfully fitted to the Redlich-Kister model.