Our objective was to investigate the efficacy of intravenous alendronate for the treatment of glucocorticoid-induced osteoporosis (GIOP) in children with autoimmune diseases. Five children with autoimmune disease and GIOP were treated with 5 mg intravenous alendronate once every 3 months. After 1 and 2 years, we evaluated the changes in the Z score of the femoral neck bone mineral density (BMD), serum bone alkaline phosphatase, and urinary deoxypyridinoline. Six patients with GIOP, whose BMD could be observed over a 1-year period without alendronate treatment, were defined as controls. After 1 and 2 years of treatment, intravenous treatment significantly inhibited bone loss. The efficacy of alendronate demonstrated a significant correlation with a high level of bone turnover markers before alendronate treatment. Intravenous alendronate is considered to be a good choice for the treatment of GIOP because of its excellent efficacy. In addition, our study suggests that the efficacy of alendronate depends on the bone turnover of patients before treatment. Intervention with bisphosphonates during periods of high bone turnover may be recommended.