The pot experiment was conducted in Horticulture Research Institute (HRI), Agricultural Research Center, Giza, Egypt during two successive seasons of 2020 and 2021 to study the effect of basil leaves extract (BLE) on growth, chemical composition and different properties for essential oil of Eucalyptus citriodora seedlings under different irrigation intervals. Results clarified that the vegetative growth parameters and photosynthetic pigments were increased in plants that were irrigated every 6 days but proline and MDA were decreased at the same treatment. While, leaf area showed high increment in plants irrigated every 4 days, whereas, all root traits, total sugars content in all organs and antioxidant enzymes activity (PPO, SOD, POD and CAT) were raised by irrigation intervals every 8 days. E. citriodora plants sprayed with BLE at rate 20% produced the highest value for all vegetative growth parameters and all chemical compositions except proline and MDA which showed the lowest value at the same rate. Irrigation every 6 or 8 days with spraying 20 or 40 % of BLE was the best treatments for production of essential oil fresh leaves. Main constituent of essential oil of Eucalyptus citriodora fresh leaves is citronellal which reached to 71.54% by irrigation every 8 days with spraying 40% of BLE, the oil was monoterpenoid 92.59- 97.93%. Oil and its major monoterpenes exhibited restrained to strong antioxidant activity.