Oxidative instability represents a critical barrier to the practical application of essential oils as functional additives in aquaculture feeds. This study evaluated the oxidative resistance of three commercially relevant essential oils: cinnamon leaf (Cinnamomum verum), peppermint (Mentha piperita), and tea tree (Melaleuca alternifolia), under conditions simulating feed processing and storage, including UV-C radiation (254 nm) and elevated temperature (60 ºC) for up to 48 hours. Chemical composition was determined by GC-MS, and lipid peroxidation was quantified by malondialdehyde (MDA) accumulation using the TBARS method. The results revealed a clear relationship between chemical profile and oxidative stability. Tea tree oil exhibited greater oxidative resistance, with lower MDA levels compared to cinnamon leaf and peppermint oils after 48 hours of thermal and UV stress (p < 0.05). These findings indicate that oxidative stability is a criterion for technical and economic feasibility in the selection of essential oils for aquaculture. While tea tree oil shows high potential for direct application, the use of unstable oils depends on the development of technological protection strategies, thereby redirecting research and development efforts toward economically viable formulations.