Spondylolysis is a common reason of low back pain in children and adolescents, which can be caused by some predisposing factors and also is associated with some environmental factors.On the other hand spondylodiscitis is an uncommon diagnosis in children caused by different agents and according to the configuration of the vertebrae and adjacent structures in children the mechanism of pathogenesis is different from adults.We present a case of spondylolysis and spondylodiscitis in a 3year-old girl with low back pain.