The by-product of sesame seed coats from the tahini industry was used for the extraction of bioactive compounds as novel antioxidants. This study was designed to evaluate the effect of a natural antioxidant on the quality of refined olive oil (ROO) stored at 60 ± 1 °C for up to 48 days. The lyophilized sesame seed coats extract (LSSCE) was placed into fresh ROO at three levels, i.e., 200, 400, and 600 mg kg−1, and compared with 200 mg kg−1 BHT (reference) and without antioxidant (control). LSSCE exhibited high phenolic (105.9 mg GAE g−1) and lignin (6.3 mg g−1) contents as well as antioxidant activity based on HPLC/DAD. In ROO samples, Including LSSCE, the values of peroxide, p-anisidine, K232, and K270 were remarkably lower than control during storage. The kinetic rate constant (k) of oxidation indicators was the lowest in ROO samples containing BHT and LSSCE 600 mg kg−1compared with other treatments. LSSCE improved the organoleptic acceptability of ROO samples up to 48 days of storage. Moreover, the shelf life (assuming a Q10 value of 2.0 for lipid oxidation) of ROO treated with LSSCE was increased. The findings revealed that LSSCE is a promising natural antioxidant in delaying oxidation, enhancing oil stability, and prolonging the shelf life (~475 days at ambient temperature).