A novel pea protein-based emulsifier was used in the production of oil in water (O/W) nanoemulsions. The regions of kinetically stabilized O/W emulsions were individuated in a pseudoternary diagram containing different pea protein, sunflower oil, and water fractions. The stable O/W emulsion region was widened by the addition of NaCl to the aqueous phase or, to a more significant extent, by high pressure homogenization (HPH) processing. The HPH treatment caused the formation of very fine emulsions in the nanometric range (<200 nm), with extremely high stability over time. HPH treatment affected the protein properties, resulting in a reduced water surface tension. Changes in protein structure, which were characterized by light scattering and SDS-PAGE, suggest the occurrence of the disruption of disulfide bonds, thus changing the exposition and availability of hydrophobic groups.