Olive is an important fruit species used for the production of table olives as well as olive oil. Due to the process of mechanical oil extraction, olive oil maintains a unique fatty acid and phenolic profile, which has recognized health benefits, putting olive oil on the list of functional foods. In addition to other agro-ecological and technological factors, fertilization treatments and the olive tree cultivar are some of the factors that have a significant impact on olive fruit yield and the composition and quality of olive oil., It has been found that excessive nitrogen fertilization leads to changed oil composition, affecting its phenolic profile, bitterness and stability. On the other hand, the role of sulphur on the yield and olive oil quality remains largely unknown. However, sulphur has been extensively studied in other oil crops due to its physiological role in lipid synthesis, where it was shown to improve the yield as well as the olive fruit oil content and the composition of oil. Sulphur and nitrogen are known to positively interact, facilitating the process of their uptake and integration into organic molecules. Sulphur-based foliar fertilizers therefore usually contain nitrogen. The aim of this study was to determine the role of sulphur and nitrogen foliar treatments in two phenophases of fruit growth on the quantitative and qualitative characteristics of virgin olive oil. Foliar treatments were applied during 2019 and 2020 on the selected, comparable trees of two cultivars: ‘Leccino’ and ‘Istarska bjelica’. The impact of the treatments on the nutritional status of the tree and morphological features of the fruit were examined. The results show that the applied foliar treatments increased sulphur content in the olive tree leaf, without increasing the nitrogen content in the dry matter, when compared to the control treatment. Sulphur and nitrogen treatments resulted in a somewhat increased fruit yield per tree by improving morphological features of the fruit. The oil randman was affected by the foliar treatments and the olive tree cultivar, with 'Istarska bjelica' measuring a higher randman than 'Leccino' in the both observed years. Although sulphur and nitrogen foliar treatments had a small effect on the main olive oil quality variables, they did not result in the change of the category of oil, with all of the oils remaining in the “extra virgin olive oil” category. The olive tree cultivar proved to be a strong predictor of the total phenolic content in the oil in both years, while the treatments had no effect on the total phenolic content of the studied samples. The results indicate that foliar treatments with sulphur and nitrogen can improve morphological features of the fruit without negatively affecting the quality of the virgin olive oil. The results contribute to a better understanding of the physiological role of sulphur in olive cultivation. The shown effects of foliar treatments with sulphur and nitrogen warrant their widespread use as a standard agronomic practice in olive cultivation.