Fish oil is highly susceptible to lipid oxidation, which leads to safety loss during storage. Natural antioxidants can prevent lipid oxidation. Satureja bachtiarica Bunge, also known as savory, is an endemic species plant that contains the necessary bioactive compounds and possesses antioxidant activity suitable for this purpose. This study featured the effects of savory extract and its essential oil as stabilizing agents on kilka fish oil. We assessed the oxidative stability of fish oil fortified with of savory extract and essential oil in amounts of 0.5 and 1%. Then we compared their oxidative activity with that of samples treated with a synthetic antioxidant during 35 days at 40°C. The fish oil samples were tested for antioxidant activity, acid degree value, thiobarbituric acid-reactive substances, para-anisidine value, conjugated dienoic acids, peroxide value, total oxidation value, and free fatty acids. Savory essential oil at the concentration of 1% was more effective than other samples in reducing the rate of lipid oxidation in fish oil. On storage day 35, the control sample yielded the following data: peroxide value = 14.79 meq O2/kg, acid degree value = 32.49 mL/g, thiobarbituric acid-reactive substances = 5.82 mg MDA/g, para-anisidine value = 116.03, total oxidation index = 136.27. These results were significantly (p < 0.05) higher than those in the sample with 1 % savory essential oil: peroxide value = 9.52 meq O2/kg, acid degree value = 22.41 mL/g, thiobarbituric acid-reactive substances = 3.46 mg MDA/g, para-anisidine value = 78.3, total oxidation index = 108.09. The fish oil samples contained more unsaturated fatty acids (66.76–68.83%) than saturated fatty acids (31.13–32.6%). Savory essential oil demonstrated good potential as an effective natural antioxidant that extends the shelf life of fish oil.