Spontaneous improvement (SI) occurs more frequently in children with chronic immune thrombocytopenia (cITP) than in adults. It is generally accepted that, with the exception of splenectomy, conventional medical approaches for cITP do not change the natural course of the disease. Previous studies on pediatric cITP have reported prognostic factors associated with SI; however, it is important to know when such improvement occurs to enable optimal treatment strategies for cITP. Here, we report results of retrospective analysis of 56 consecutive pediatric patients with cITP at our institution. The median follow-up period after ITP diagnosis was 67 months (11-185 months). Of the 44 patients without splenectomy, 17 achieved SI at a median age of 8.5 years (2.3-16.5 years). The estimated incidence of SI was 24.6 ± 6.0 % at 36 months. In 16 of the 17 patients with SI, the recovery was achieved within 18 months from diagnosis, or at an age of less than 10 years, whereas among the 24 who did not achieve spontaneous improvement both at "an age of 10 years or more" and at "18 months or more from ITP diagnosis", only one recovered spontaneously. A treatment decision tree, including the indication for splenectomy, should be considered based on this watershed point.