SummaryThis study evaluates physical and chemical stability of ultrasound‐assisted grape seed oil primary emulsions stabilised by varying compositions of caseins to whey proteins (80:20, 60:40, 50:50 and 40:60) at different sono‐operating conditions (81.9 and 117.0 J mL−1). Physical and chemical stabilities were influenced by both sonication energy densities and milk protein compositions. Emulsions prepared at 81.9 J mL−1 energy density with ≥40% whey protein fraction (60:40, 50:50, 40:60 and WPI) showed greater physical stability than the emulsions sonicated at 117.0 J mL−1 which exhibited physical instability due to the depletion flocculation mechanism at the critical casein concentration (≥40%). The emulsion oxidative stability was found to be affected by sonication conditions as 117.0 J mL−1 induced the oxidation reactions once the whey concentration exceeds 40%. Therefore, ultrasound prepared emulsions with casein to whey ratios of 60:40, 50:50, 40:60 and WPI at 81.9 J mL−1 energy density was found to be stable for 10 days at 4 °C.