This study aimed to determine the antioxidant activity of Borago officinalis essential oil in the thermal oxidation of fish oil. The volatile compound profile of B. officinalis essential oil (BEO) was determined using gas chromatography and mass spectrometry. As a result of the analysis, 97.27 percent of the volatile components of the product were characterized. The product’s major components were benzene acetaldehyde (28.59 percent) and linalool (13.60 percent). As a result of the free radical scavenging activity determined using 2-diphenyl-1-picrylhydrazyl (DPPH) analysis, its antioxidant activity was determined, and a 50 percent inhibitory concentration value was calculated as 736.06 ppm. In order to determine the protective effect of the BEO on fish oil oxidation, 0% (BEO0), 0.1% (BEO0.1), 0.5% (BEO0.5), 1% (BEO1), and 3% (BEO3) ratios of BEO were added to the fish oil, and the experimental groups were kept at 70 °C for 24 h with continuous ventilation for the thermal oxidation process. As a result of the oxidation study, it was determined that the addition of BEO suppressed fish oil oxidation, and the oxidation radicals in the product decreased significantly (p < 0.05) depending on the BEO concentration. In conclusion, it was determined that 1 percent BEO supplementation minimized the oxidation of fish oil under various temperature and ventilation conditions.