Abstract: Background and Objective: Cereal Cyst Nematodes (CCNs) Heterodera avenae are from the most critical nematode pests that restrict the production of cereals worldwide. These nematodes alone are savage pests that harm wheat and reduce their production by 10(%) globally. This study was done to study the changes in the physiological and biochemical activity of wheat plants infected with nematodes. Materials and Methods: The pot experiments were conducted in the greenhouse of the National Research Centre, Dokki, Cairo, Egypt. Wheat seeds variety Misr-1 was used. Treated pots were infested with nematode cysts to give a population density of 8000 j2 and eggs 1 kg–1 soil. The roots and shoots of seedlings were processed for physiological and biochemical analysis. The mean comparisons among treatments were determined by Duncan’s multiple range tests at a 5(%) level of probability. Results: Our results proved the promotion effects of CCN on Reactive Oxygen Species ROS as Malondialdehyde MDA production that concomitant with the inhibitory effects on photosynthetic pigment contents, altering endogenous phytohormones, Indole-3-Acetic Acid (IAA), Abscisic Acid (ABA), Gibberellic Acid (Gas), Zeatin and reconstructing the production of assimilates (Total Soluble Solids (TSS), total carbohydrates and protein). These variations stimulate the production of enzymatic antioxidants, Superoxide Dismutase (SOD), Catalase (CAT) and Peroxidase (POX) and non-enzymatic antioxidant, phenol. The infection also affects the absorption and translocation, production of minerals, P, K, Fe, Zn, Mn and Cu. All of these changes reflected on the yield production and the nutritional values of yielded grain grown under such conditions. Conclusion: Most nutritional values, physiological and biochemical aspects of wheat decreased in the infected plants as compared with non-infected plants.