Background and aims Patients affected by metastatic germ cell tumors may occasionally experience enlargement of metastatic lesions with concurrent normalization of tumor markers after chemotherapy. This phenomenon is described as Growing Teratoma Syndrome (GTS). The aim of the present study is to assess the prevalence of GTS in the pediatric population and its implications in terms of surgical outcome. Methods The clinical notes of patients diagnosed with stage III and IV malignant germ cell tumors from January 2010 until December 2020 at our Institution were retrospectively reviewed. Patients with residual disease after chemotherapy were studied; the occurrence of GTS, treatment strategies, survival and outcome were analyzed. Results Thirty-three patients with high stage malignant germ cell tumors were diagnosed in our Institution in the analyzed period. Eleven patients (34%) had radiologic evidence of enlargement of metastases after chemotherapy; nine of them (28%) had normal markers after chemotherapy and were classified as GTS patients. All nine patients underwent resection of metastatic lymph nodes and six had surgery on visceral metastases. In six patients, radical excision of all metastatic sites was achieved; five patients are alive and in complete remission while one died for peri-operative complications. Out of the three patients who could not achieve radical excision of the metastases, two died for progressive disease and one is alive with progressive disease. Conclusions Patients affected by GTS have a risk of progression of chemotherapy-resistant disease and death. Radical surgical excision is essential to achieve disease control and long-term survival.