Sunflower oils obtained after frying potatoes for different times (1, 5, and 10) and non-fried oils were analyzed. In total, 43 aroma substances were identified by GC-MS analyses and aldehydes were detected as the main chemical group. The concentration of aldehydes increased with the frying process and among them, (E,E)-2,4-decadienal, (E)-2-heptenal, and hexanal were found to be the major aroma compounds. High performance liquid chromatography with diode array detector, coupled with mass in tandem mode, were employed for quantitative and qualitative analysis of phenolic compounds. Rutin was the major phenolic compound in sunflower oils followed by chlorogenic acid, and they constituted the largest proportion of the total phenolic content in all oil samples. The concentration of phenolic compounds of sunflower oil revealed essential changes during several thermal processes and underwent degradation during heating. Only about 2% of its initial content presented after 10 frying process. Practical applications The present study explores the effects of the deep-fat frying process on aroma and phenolic compositions of sunflower oil. The cooking technique plays a significant role in the expanding global food industry. The findings of the research could be helpful for standardizing and preserving the taste, aroma, and nutritional value of the used oils and foods. Additionally, for the researchers, this study would give insight for identification and qualification phenolic and aroma compounds of sunflower oil.