Fennel (Foeniculum vulgare Mill.) is one of the most important spice plants produced commercially. In addition to having a degassing property, fennel is also a plant which is rich in odor, taste and essential oil and it is also used widely as spice. This study was carried out in Dumlupınar University, Medicinal and Aromatic Plants Department’s application field in 2017 in order to determine the effect of different boron doses (boron free, pure boron with 8 liters per decares and in 1/8 ratio diluted boron) on the rate and quality of volatile oil found in fennel (Foeniculum vulgare Mill.) in Kütahya-Gediz conditions. Field experiments were administered as 3 replicates according to randomized block design in 2017. The volatile oil composition was determined by Gas Chromatography-Mass Spectrometry (GC-MS). Essential oil ratios were found as 1.83%, 3.43% and 1.55%, for no boron dose, pure dose and 1/8 boron dose, respectively. 7 components were found in each analyse which was carried out on fruits of the fennels which were grown with 3 different doses (no boron, pure dose and 1/8 dose). The main components in the volatile oil obtained without boron use are as follows; trans- anethole 84.65%, limonene 5.92%, p-allylanisole 4.18 % and fenchone 1.12%. The components obtained in the pure dose were found as follows; trans-anethole 94.52%, anisole 3.54%, limonene 1.09%, fenchone 0.36% and in 1/8 dose the rates are as follows; trans-anethole 92.38%, anisole 3.8%, limonene 2. 85%, fenchone 0.35%.