Whey protein is a valuable by-product of cheese making because of its highly nutritional value and some desirable functional properties. The objectives of this study were to prepare liquid whey protein (LWP) concentrate solution using membrane technology from Cheddar cheese whey, to polymerize whey proteins in the solution, and to use the polymerized whey protein (PWP) as a thickening agent for yogurt formulation. Fresh whey collected from cheese vat was pasteurized (60°C for 30 min) and pre-filtrated using screen mesh. The treated whey was subjected to microfiltration (0.1 µm, at 45°C for 1 h). The microfiltrated whey was ultrafiltered using a 10-kDa cut-off membrane to about 20-fold. The UF treated whey was electrodialyzed (ED) to remove 90% of salt. The final protein content of the liquid whey protein (LWP) concentrate was 8.0%. The obtained liquid whey protein concentrate (8% protein) and WPC solution of same protein content were heated at 85°C for 30 min at pH 7.0. The particle size and zeta potential of PWP prepared from LWP was similar to those of PWP prepared from commercial whey protein concentrate (WPC80). Addition of PWP significantly (P < 0.05) increased the viscosity of the yogurt samples, whereas addition of polymerized LWP did not significantly affect the viscosity compared with the control. There were no differences in pH, TS, ash, fat, protein, and lactose contents among the yogurt samples (P > 0.05). This new technology of preparing PWP directly from liquid whey protein concentrate through membrane separation technology can be used as gelation agent for yogurt making. This product (PWP) could be also used as a natural and functional ingredient for formulation of milk based fermented foods.