For applications of block copolymer mixtures as potential new nano-vehicles for delivery, understanding the components mixing characteristics are of special interest. In our previous study , we showed that interactions between a biological charged diblock-copolymer like protein, beta-casein, and a synthetic uncharged synthetic triblock copolymer, Lutrol F-127, lead to the formation of mixed micelles. Here we report on synergistic effects found in some mixing ratios, and the mixed micellization characteristics, obtained by Isothermal Titration Calorimetry (ITC), Cryogenic-Transmission Electron Microscopy (cryo-TEM), Small-Angle X-Ray Scattering (SAXS) and Dynamic Light Scattering (DLS). At low Lutrol mole fractions we have observed a complicated micellization process characterized by two critical mixed micelles concentrations (CmMC). Positive and negative synergistic effects of Lutrol were revealed.