Complex coacervation between whey proteins isolate (WPI) and Acacia gum was investigated in order to disclose the roles and the contributions of each component of WPI to the formation of the complex coacervate. The main aim was to establish the balance of the main components of WPI, beta-lactoglobulin and alpha-lactalbumin, during the phase separation of complex coacervate. The complex coacervation of Acacia gum and pure beta-lactoglobulin, pure alpha-lactalbumin, and WPI have been investigated and compared together by means of macroscopic observations and capillary gel electrophoresis analyses performed along pH scans from basic to acidic medium. Coacervate composition was influenced by the protein/polysaccharide (Pr: Ps) ratio and pH. An optimum pH for best coacervation yield was found for each Pr: Ps ratio. Non-negligible concentrations of beta-lactoglobulin and alpha-lactalbumin remain in solution in most instances. beta-lactoglobulin undergoes complex coacervation stronger than alpha-lactalbumin in their competitive coacervation of WPI and Acacia gum.