Purpose This study was designed to evaluate the effectiveness of conservative treatment for chylous leak after tumor surgery and to propose a management algorithm. Methods The data of patients with postoperative chylous leak after tumor surgery in our institution between 2010 and 2019 were retrospectively reviewed. In this study, 469 laparotomies, 89 thoracotomies, and 57 cervical excisions were performed for tumor surgery in our institution. Results Twelve patients with a median age of 4 (IQR, 3-8) years had postoperative chylous leak. All patients received total parenteral nutrition for a median of 13 days. Five patients had intravenous somatostatin for a median of 14 days (IQR, 9-16) to decrease chyle production. Eventually, chylous leak ceased in all patients with conservative treatment and surgical drains were removed after no leak was observed with enteral feeding. Conclusions The incidence of chylous leak in childhood tumor surgery is approximately 2%. Extended tumor resection and lymph node dissection lead to the injury of the delicate structures that drain chyle. Conservative treatment with total parenteral nutrition and somatostatin seems to be effective. In particular, somatostatin may be used in resistant cases. Conservative treatment can take up to 1 month. The algorithm consists of how to manage postoperative chylous leak in childhood.