This study was designed to determine adverse effect of nitrite on some hematobiochemical parameters and egg production in laying hens. Sample from underground well water from different region in Sharkia province (Diarp Negm, Kafr Sakr, El Salhia and Zagazig) was examined for detection nitrite level. Analysis of water sample revealed presence of nitrite in level of 0.34, 0.013, 0.05 and 0.63 ppm nitrite in Zagazig, Diarp Negm, Kafr Saker and El Salhia Cities. A total of 60 laying hens (22 week age) were divided into 3 equal groups (20 of each). First group laying hens received one liter of water contains 1mg nitrite/liter for 30 day  (control group), second group laying hens received one liter  of water contains 4mg nitrite/lite for 30 day and third group laying hens received one liter of water contains 8mg nitrite/lite for 30 days. At 1^st day post supplementation three blood samples were collected from 5 birds for hematobiochemical study. Hens received one liter of water contains 4mg sodium nitrite/liter drinking water for 30 days showed non-significant reduction in RBCs, Hb, PCV, MCHC, WBCs, lymphocyte, Phagocytosis, total protein, albumin, globulin and egg production and Calcium beside insignificant increase in MCV, MCH, Platelet count, heterophils, AST, ALT, ALP, uric acid and creatinine. Meanwhile hens received one liter of water contains  8 mg nitrite/liter show significant reduction in RBCs, Hb, PCV, MCHC, WBCs, lymphocyte, Phagocytosis, total protein, albumin, globulin, egg production%, egg weight, Shell thicknes, Egg shell weight and Calcium beside significant increase in MCV, MCH, Platelet count, heterophils, AST, ALT, ALP, uric acid and creatinine. Residues of nitrite in liver and kidney beside its dose dependent laying hens received one liter of water contains 0.1% sodium nitrite showed normal histological structures in all body organs (liver, Kidney and spleen) but laying hens received one liter of water contains 4% and one liter of water contains 8% sodium nitrite showed moderate to severe lesion in liver, Kidney and spleen. It could be concluded that high nitrite in water induce alterations in hematobiochemical parameters and egg production as well as pathological lesions. So, it is recommended not use water contains high level of nitrite in laying hens farms.