Daucus carota L. (Apiaceae) is an important vegetable crop cultivated worldwide for its nutritive roots. The aim of this study was to examine changes occurring in the essential oil yield and chemical composition of D. carota L. subsp. sativus (Hoffm.) Arcang. ‘umbels’ during flowering and fruiting process. The essential oil yield varied from 0.7% to 1.8% (v/w) during umbel ontogeny. The resulted essential oils were analysed by gas chromatography–flame ionization detector (GC–FID) and GC–mass spectrometry (GC–MS). Altogether, 34 constituents, forming 94.5–97.9% of the total compositions were identified. The essential oil composition was characterized by high proportions of monoterpenoids (35.9–81.3%) and sesquiterpenoids (15.1–62.0%). Major constituents of the essential oils were carotol (10.2–58.5%), α-pinene (21.2–41.2%), myrcene (6.4–14.1%), limonene (4.4–12.7%), and sabinene (0.2–5.3%). The results obtained are of significance for determining the most favorable time for harvesting carrot umbels for better yield of quality essential oil.