Structural, physical and emulsifying properties of native (control) and whey protein (WP) fibrils were evaluated after using different mechanical processes or energy densities. Fibrils were prepared at pH 2 but the increase of pH to 7 led to the fibril aggregation. When subjected to mechanical processes, the increase in energy density led to fibril shortening and reduced aggregates of fibrils for systems at pH 2 and 7, respectively. Mechanical processes did not affect significantly the protein secondary structure conformation and interfacial tension at aqueous protein dispersion-oil interface. However, increasing fibril pH resulted in decreased surface hydrophobicity and interfacial tension and loss of ordered secondary structure. Dispersions of native proteins showed Newtonian behavior while fibril dispersions showed shear-thinning (at both pH values) and thixotropic behavior (only at pH 7). Emulsions stabilized by fibrils at pH 2 showed low kinetic stability but, different from control systems, they did not present further destabilization mechanism after the equilibrium creaming index was reached. Emulsions with fibrils at pH 7 showed no phase separation or a slower destabilization probably due to high viscosity and great decrease of interfacial tension, resulting in steric hindrance stabilization and faster migration of these fibrils to the interface when compared to fibrils at low pH. Therefore, modifying WP by mechanical processes resulted in varied emulsifying properties depending on the pH and protein conformation.