The nutritional benefits of polyunsaturated fatty acids from fish oil in terms of their role in growth and development and in health and disease are limited by their oxidative degradation. The objective of this study was to investigate the effect of bovine and caprine caseins in combination with phospholipids on the oxidative stability of 5% fish oil-in-water emulsions at pH 7.0. Menhaden oil was emulsified with phospholipids such as phosphatidylcholine, phosphatidylethanolamine, and phosphatidylserine in a high-pressure valve homogenizer. The effect of bovine and caprine caseins in combination with phospholipids on oxidation rate was monitored by measurement of thiobarbituric acid reactive substances (TBARS) and lipid peroxides. Oxidation of 0.5% phospholipid-stabilized fish oil-in-water emulsions were performed at 25°C for 48 h, in the dark, in the presence of 0–0.3% bovine and caprine caseins and 0.1 mM Fe²⁺. It was found that the emulsion stabilized with phosphatidylserine showed the best oxidative stability in terms of TBARS concentration and peroxide value. Formation of TBARS was inhibited 32% by addition of 0.3% caprine casein (P < 0.05). Inhibition of lipid oxidation by addition of 0.3% bovine casein was less effective, decreasing the concentration of TBARS by 24% (P < 0.05). The combination of casein and phosphatidylserine resulted in favorable structure and thickness of the interfacial layer, thus preventing lipid oxidation in the emulsion. These results indicated that the combination of casein and phosphatidylserine can be utilized to enhance the oxidative stability of emulsified fish oil.