To study the phase equilibrium in {ionic liquid, 1-butyl-3-methyl imidazolium chloride + poly(propylene glycol) 400, or poly(ethylene glycol) dimethyl ether 250 + water} solutions, vapor-liquid equilibrium data for these systems were determined at T = 298.15 K. To model the water activity data, the Wilson, modified Wilson, nonrandom two liquid (NRTL), and modified NRTL models were applied. Vapor pressure depression data were used to investigate the hydration of studied polymers in aqueous media. Furthermore, to discuss the salting effect of the studied ionic liquid on aqueous polymer solutions, Gibbs energies of transfer of polymers from water to aqueous ionic liquid solutions were computed. The positive and increasing values of Gibbs energies of transfer with the increase in ionic liquid concentration indicate that this ionic liquid has a salting-out effect on aqueous polymer solutions, which means that there are unfavorable interactions between the ionic liquid and studied polymers. These results are consistent with the aqueous two-phase system formation of the studied ionic liquid on both polymers in aqueous media.