A field experiment was carried out during the summer seasons of 2018 and 2019 at Gemmeiza Agric. Res. Station, Gharbeya Governorate, Egypt to evaluate effects of mineral and organic nitrogen as well as using vitamin C and chitosan as foliar spray on growth, yield and fruit quality of sweet pepper cv. California Wonder grown in clay soil. The interaction between fertilizing sweet pepper plant with MN at 25% RR+ ON at 75 % RR and spraying with Vit. C at 300 ppm increased plant height, number of leaves / plant, number of branches/ plant and shoot dry weight at 90 days after transplanting in both growing seasons. However, fertilizing plants with MN at 25% RR + ON at 75% RR and spraying with chitosan at 2ml/l or Vit. C at300 ppm increased N, P and K contents and their uptake by shoot. In addition, the interaction between fertilizing with MN at 25 % RR+ON at 75 % RR and spraying with chitosan at 2 ml/l increased average fruit weight, yield/plant and total yield /fed. as well as nitrogen use efficiency and lowest values of nitrate content in fruits. Nevertheless, the interaction between fertilization with MN at 50% RR + ON at 50% RR and spraying with chitosan at 2 ml/l increased DM% in fruit, whereas the interaction between fertilizing with MN at 50 %RR+ON at 50 %RR and spraying with Vit. C at 300 ppm increased TSS and Vit. C in fruits in both seasons.