Effects of Lepidium perfoliatum seed gum (LPSG) concentration (0, 0.3 and 0.6 wt%) and different processing treatments (freezing, pasteurization and sterilization) on physical and stability of oil-inwater emulsion prepared by whey protein (6 wt%) was investigated. For this purpose, particle size distribution, creaming index, microscopic characteristics, viscosity and flow behavior of emulsions were studied. Results showed that thermal processing increased the particle size of dispersed phase. Results also showed that the damage of membrane surface at high temperature such as sterilization was higher than other temperatures. At low Lepidium perfoliatum seed gum concentration, the emulsions were somewhat more resistant to thermal processes. However, at higher gum concentrations (0.3 and 0.6%), thermal processing did not have a negative effect on the emulsion stability. The viscosity and consistency coefficients also increased with increasing gum concentration. Shear thinning behavior for emulsions at all thermal treatments were also observed. Therefore, adding LPSG to the emulsion could increase its stability to the thermal processing.