A pot experiment was conducted for two successive seasons to evaluate the effect of cobalt on sunflower growth, yield and essential oil percent. Experiment was conducted at a cage house , National Research Centre , Dokki ,Giza .Egypt. Plastic pots 50 cm diameter  of  ten kg soil capacity were used. Sunflower seeds were sown at  7^th and 9^th March   of during 2018 and 2019. Seedlings (at the third true leaf) were irrigated with cobalt, sulphate once, with different cobalt doses (7.5 , 10.0 , 12.5 , 15.0 , 17.5 , and 20.0 mgL^-1). All cobalt levels has a significant enhancing effect on plant growth, yield and essential oil contents. Cobalt at rate of 12.5 mgL^-1 resulted the greatest effect. As cobalt level in plant media increased more than 12.5 mgL^-1, the promotive effect was reduced. All levels of cobalt increased contents of (N, P and K) as well as (Mn, Zn and Cu) in seeds. As cobalt increased in plant media, cobalt content in sunflower seeds increased ,wherease Fe content was decreased.