Two field experiments were conducted in 2016 and 2017 growing seasons under natural infection of basil downy mildew in the Experimental Farm of Sids Agricultural Research Station, Agric. Res. Center, Beni-Sweif governorate to examine the impact of sowing dates on basil downy mildew epidemic caused by Peronospora belbahrii and productivity of basil plant. Sweet basil seeds were sown in different dates, early date (February), mid date (March) and late date (April). In general, early sowing significantly gave lower disease incidence and severity than late sowing. Although the early sowing dates (February) gave the highest reduction in disease incidence and severity but drastically affected plant growth and yield to the lowest value. The highest efficacy was obtained when sweet basil seeds were sown in March 15th which significantly decreased the incidence and severity of downy mildew to an important level and consequently, increased fresh and dry yields of herb.