In this work, we used an aqueous two-phase system (ATPS) consisting of the ionic liquid [C(4)mim][Cl] and the salt K2HPO4 to partition alpha-lactalbumin, beta-lactoglobulin, and lactoferrin whey proteins. Extraction efficiency values above 87% indicate that the proteins primarily migrated to the ionic liquid-rich phase (top phase). Partition coefficient values ranged from 6.17 to 8.93 for alpha-lactalbumin, from 22.80 to 34.55 for beta-lactoglobulin, and from 26.46 to 40.06 for lactoferrin. Therefore, the saline ATPS with the ionic liquid examined in this study can be considered to be a promising alternative for extracting whey proteins.