This research was carried out to estimate the genetic variance components for sunflower fatty acids in two separate optimum and drought stressed conditions in Karaj during 2020 and 2021 growing seasons. The plant materials consisted of 12 hybrids derived from crossing of four restorer lines by three cytoplasmic male sterile lines (Testers) that were evaluated in two separate experiments as randomized complete block design with three replications. Drought stress made a reduction in oil yield (34 percent), oil content (six percent), stearic acid (4.7 percent) and oleic acid (10.6 percent) and an increase in palmitic acid (12 percent) and linoleic acid (2.8 percent). Line × tester interaction effect had a major role in explanation of the variance of the hybrids in terms of fatty acid content in both conditions, indicating the critical role of non-additive effects in genetic control of these traits. Under optimum irrigation, oil yield, oil content and stearic acid content were under control of both additive and dominant gene action and palmitic, oleic and linoleic acids were under control of dominant gene action. Under drought stress, except oil content which was under control of additive effects, all the other traits were under control of dominant gene action. According to the results of this study, fatty acid composition of sunflower was under control of non-additive genetic effects and the crossing-based methods and hybrid breeding could be used for improvement of sunflower in terms of fatty acid composition.