This study was carried out in three phases. During the first stage, the physicochemical properties of French sauce prepared from different blends of soybean and olive oils were evaluated. In the second stage, the oxidative stability of the optimum sauce sample from the first stage enriched with various amounts of olive leaf polyphenolic extract (OLE) (obtained via ultrasound-assisted extraction) was investigated over 90 days of storage. During the third stage, the microbiological and sensory properties of the samples containing the optimum amounts of OLE, as a substitution for the synthetic preservatives, were studied. According to the results, addition of olive oil at higher levels (75 and 100%) could affect the physicochemical properties of the sauce as compared to the control sample. It was also found that the addition of olive oil (up to 50%) would not significantly impact the sauce properties. Regarding the OLE enrichment in the samples, it was found that high levels of OLE could improve the oxidative stability of the samples. Based on the results of the experiments in the third phase, it was found that OLE could be used as a preservative instead of the commercial ones. Overall, this study suggests the potential use of olive oil and olive leaf extract in the preparation of French sauce to boost its nutritional value and its stability.