Cypress trees (Cupressus sempervirens L.) are an exotic species introduced to Yemen. Fusarium oxysporum has been identified as the causal organism of wilt disease widely spread in the country. Phytotoxicity of Fusarium oxysporum culture filtrate has been tested on cypress branchlets, seedlings and seed germination. It was found that water up-take by branchlets and seedlings were significantly reduced when grown in of F. oxysporum culture filtrate. Symptoms development of wilt disease was confirmed on cypress seedlings grown in pots treated with different concentrations of Fusarium oxysporum culture filtrate. The impact was concentration independent. Though toxic effect of the culture filtrate was not affected by autoclaving, it slightly delayed wilt symptoms development. Germination percentage of cypress seeds was also reduced significantly by F oxysporum culture filtrate. The impact again was concentration independent.