Celecoxib is increasingly being used in children with rheumatologic complaints. Although the particular concerns about the safety of the drug, there are only a small number of published studies in children. This study was performed to investigate the effects of celecoxib on oxidative stress and antioxidant enzyme activities as well as celecoxib-induced changes in liver, kidneys and stomach of young rats. Four weeks-old Wistar albino, female rats were used. Celecoxib was given by gavage for 14 days. Control rats received only vehicle. Blood and organs were taken under pentobarbital anesthesia. Plasma malondialdehyde levels were increased by treatment. Catalase activity was increased, while glutathione peroxidase activity was decreased. Superoxide dismutase and glucose-6-phosphate dehydrogenase activities was not changed by treatment. The reduced glutathione content of kidneys were higher, while there was no significant difference in liver content, as compared with controls. Significant changes were observed in serum parameters of rats treated with celecoxib. Histopathological evaluation of organs was done by an experienced pathologist unaware of the treatment. Results of the present study indicated the alterations of oxidant/antioxidant status and histopathological changes in tissues of young rats treated with celecoxib.