This study is conducted to examine the effects of Tomato yellow leaf curl virus (TYLCV) geminivirus infection on nitrogenous constituents, proline, nitrate reductase, phenylalanine ammonia lyase activity, total phenol content, glutathione, lipid peroxidation (MAD) and also activities of superoxide dismutase (SOD; EC 1.15.1.1), peroxidase (POD; EC 1.11.1.7) and catalase (CAT; EC 1.11.1.6) were estimated in both healthy and infected tomato plants. Infected plants showed reduction in total protein and nitrate reductase. Besides these, TYLCV infection caused an increase of total-N, amino-N, proline content in leaves, stems and roots, and also increase of phenylalanine ammonia lyase activity, total phenol content, glutathione, lipid peroxidation and activities of antioxidant enzymes in leaves were detected compared with healthy plants.