In this study, 50 Iranian fennel landraces from different phenological types, were evaluated for their oil content and fatty acid profile. Landraces were categorized into three phenological groups: Late (180 days), Medium (140 days) and early maturity habit (110 days). The highest fatty acid content among the early, medium, and late maturity types were detected in Hamedan (19.5%), Marvdasht (23%), and Sari (21%) consequently. The highest yield of oil per square meter among the early, medium, and late maturity types were detected in Fasa (65.3 ml/m2), Meshkin Shahr (92.5 ml/m2), and Sari (71.4 ml/m2), consequently. The main component of fatty acid profile were, petroselinic/ oleic acid (52-64%), linoleic acid (26-39%), palmitic acid (0.3-4.1%), stearic acid (1.3-2.4%), linolenic acid (0.6-3.6%), and myristic acid (0.35-1.07%). It was observed that landraces with high petroselinic and oleic acid content originated from arias with a dry and warm environment, while landraces with high linoleic acid content originated from regions with a humid and cool climate. This pattern shows potential evolutionary adaption of biochemical pathways to the environmental condition. Our data showed that fennel oil contains a lower ratio of omega-6 to omega-3 fatty acids, and a higher ratio of monounsaturated to polyunsaturated and saturated fatty acids. In conclusion, our result indicated that bitter fennel, furthermore of a medicinal plant, has a high potential for oil production with a high percentage of unsaturated fatty acids, and is a good candidate as at least a new table oil crop.