Copeptin is cleared by the kidney. In patients with chronic kidney disease, plasma levels of copeptin and Arginine Vasopressin (AVP) are inversely correlated with the estimated glomerular filtration rate. To assess plasma copeptin level in children with renal impairment as a marker of diagnosis and to assess its value as an indicator of disease progression. The present study was a case control study which conducted during the period from February up to November 2020 and carried out at the pediatric nephrology unit of the pediatric department of AL-Zahraa University Hospital on 90 children who were divided into three groups, Group (1) Thirty children suffering from chronic kidney disease on conservative treatment (case group), Group (2) Thirty children suffering from chronic kidney disease on dialysis (case group), Group (3) Thirty children apparently healthy age and sex matched (control group) and Assay of serum Copeptin using enzyme-linked immunosorbent assay (ELISA) and kidney function profile was done. There was highly statistically significant increase between patient groups (I & II) and control group (I) as regard Urea, Creatinine, highly statistically significant increase between patient groups and control groups as regard plasma Copeptin and there was statistically significant negative correlation between plasma Copeptin and GRF in patients groups when compared with control group. Copeptin was highly increased in patients with chronic kidney diseases and its level increased as serum Creatinine increased and as GFR decreased. Plasma Copeptin was increased as the stage of kidney disease progressed.