Afield experiment was conducted during 2016 and 2017 in the Research Farm of Sakha Agricultural Research Station, Kafr El-Sheikh Governorate, Egypt to evaluate the mutual effect of irrigation scheduling and silica nanoparticles on Ocimum basilicum L. vegetative growth, yield, chemical composition and some water relations. Irrigation scheduling treatments were 1.2, 1.0 and 0.8 of cumulative pan evaporation (CPE) while a foliar spray of silica nanoparticles at 30, 60, 90 ppm and distilled water as a control. Results showed that 0.8 of CPE decreased vegetative growth characters, fresh and oil yield ha^-1 and transpiration rate nevertheless, increased chlorophyll content, oil% and stomatal resistance value in the two cuts of both seasons. Silica nanoparticles at 60 and 90 ppm increased all characters likely oil yield increased by 52.2% over the control. Irrigation at 1.0 of CPE with silica nanoparticles at 60 ppm recorded the highest values of vegetative growth, fresh and oil yield, chlorophyll content and oil%. The highest essential oil components were α –terpineol and linalool in plants sprayed with 60 and 90 ppm silica nanoparticles under all irrigation treatments. The greatest values of seasonal consumptive use and applied irrigation water were observed from plants treated with 1.2 of CPE while, the lowest values obtained from 0.8 of CPE. The highest values of productivity of irrigation water and water productivity were recorded after 1.0 of CPE. Finally, plants treated with 1.0 of CPE combined with silica nanoparticles at 60 ppm showed enhanced vegetative growth, fresh and oil yield, stomatal resistance value, oil components while, decreased transpiration rate. Furthermore, decreased water consumptive use 7% and applied irrigation water 5% while, increased water productivity by 24% and productivity of irrigation water by 20 % compared to 1.2 of CPE without silica nanoparticles spray.