Interfacial and emulsifying properties of potato protein isolate (PPI) have been studied to evaluate its potential application to stabilize oil/water emulsions at two pH values (2 and 8). The amount, type, and solubility of proteins and the size of aggregates have been determined in aqueous dispersion. Air water and oil-water interfacial properties (adsorption, spreading, and viscoelastic properties) have been determined as a function of concentration and pH using soluble phases of PPI The behavior of PPI stabilized oil/water emulsions has been then analyzed by droplet size distribution measurements and interfacial Concentration. PPI exhibits low solubility over a wide range of pH values, with the presence of submicrometer aggregates. The pH value exerts a negligible effect on interfacial tension (oil water) or surface pressure (air water) but displays very important difference in viscoelastic properties of the interfacial films formed between oil and water. In this sense, pH 8 provides a major elastic response at Oil Water interfaces as compared to pH 2. In relation with this result, a much higher ability to produce fine and stable emulsions is noticed at pH 8 as compared to pH 2. Consequently, there is an evident relationship between the theological properties of the oil water interfacial films and the macroscopic emulsion behavior.