Binodal data for the 1-ethyl-3-methylimidazolium dimethyl phosphate ([Emim]DMP) + salt (K3PO4, K2HPO4, and K2CO3) + H2O systems were experimentally determined at T = (298.15, 308.15, and 318.15) K, respectively. The Merchuk equation was used to correlate the binodal data. The abilities of the different salts for phase separation follow the order K3PO4 > K2HPO4 > K2CO3, which may be related to the Gibbs free energy of hydration of the ions (Delta(hyd)G). The two-phase area expands with a decrease in temperature, whereas the slope of the tie lines slightly decreases with an increase in temperature. The reliability of the calculation method and corresponding tie-line data was described by the Othmer-Tobias and Bancroft equations, as well as the two-parameter equation. [Emim]DMP is a familiar ionic liquid, extensively used for the extractive desulfurization of fuel oils. This study is the first to report data on the phase diagrams of [Emim]DMP + salt + water systems.