Nickel (Ni) is as an essential micronutrient for plant that is required at low concentration for optimum plant growth. Urea is an important nitrogen fertilizer in today’s agriculture and its suitability for field crops has been well evaluated. Our knowledge of the complete biological significance of nickel for plant productivity is still quite limited. However, with the demonstration of the essentiality of nickel in different plant species and the increased use of urea as a nitrogen source, the importance of understanding the chemistry and biology of nickel and its potential impact on agricultural production and too biological effects of different level (deficiency to toxicity) on oxidative stress and anti oxidative response of plant particularly vegetables has never been greater. This work, therefore, was designed to study the impact of different level of nickel and nitrogen source on yield, some fruit quality attributes and anti oxidative capacity of two cucumber cultivars ( Cucumis Sativus L.cvs. Negin (greenhouse) and Super Dominus (field) as one of the freshly and consumed leafy vegetables. In this study, nitrogen was supplied with urea or nitrate ammonium. Four levels of Ni were (0, 50,100 and 200 µM Ni as NiCl 2 ). The plants harvested in two steps. One step was (50 day after seed germination) and two step was (100 day after seed germination). In any step fresh weight of shoots and roots were determined. Cucumber fruits was also harvested significance for determine the some fruit quality attributes. The urea concentration, urease enzymatic activity in the leaves, shoot Fe, Zn and Ni contents, antioxidants enzymatic activity (CAT, APX and GPX), MDA concentration (lipid per oxidation) and some fruit quality attributes (ascorbic acid concentration, Total soluble solids and fruit firmness) were measured. The results of this study indicated that in Super Dominus cultivar, regardless N source, Ni at 50 µM level had no effect on the root, shoot and fruit dry matter. In Negin cultivar, addition of 50 µM Ni increased root, Shoots and fruit dry matter yield in comparison with free-Ni treatment significantly although stimulating effect was greater in the urea-fed plants than the NH 4 NO 3 -fed plants. In two cucumber cultivars increased of nickel concentration to 100 and 200 µM decreased root, shoots and fruit dry matter yield and anti oxidative capacity of cucumber. In cucumber cultivars, regardless N source, addition of 50µM Ni increased urease enzymatic activity and decreased urea concentration in the leaves significantly. The effect of high level of Ni on urea concentration and urease enzymatic activity is adversely. In tow cucmber cultivars, the highest of fruit fresh matter yield, total soluble solids and fruit firmness was found at 50 µM Ni. In two cucumber cultivars, regardless N source, addition of 50 µM Ni in nutrient solution increased ascorbic acid concentration in comparison with the free-Ni treatment. According to the results, the effects of both sufficiency and toxicity levels of Ni on plant growth and yield of cucumber was dependent on the cultivars and nitrogen sources