Introduction: Data regarding coronavirus disease 2019 (COVID-19) description are still limited in pediatric oncology. The French society of pediatric oncology (SFCE) has initiated a study to better describe the presentation and evolution of COVID-19 in patients followed in French pediatric oncology and hematology wards. Methods: All patients diagnosed with COVID-19 (polymerase chain reaction [PCR] positive for severe acute respiratory syndrome coronavirus 2 [SARS-CoV-2], or positive IgM serology, or chest computed tomography scan and clinical signs typical of COVID-19) and followed in a SFCE center were enrolled. Data from medical records were analyzed for all patients enrolled up to the end of May 2020. Results: Data was available for 37 patients. Thirty-one were children under 18 years of age. Nineteen patients were female. Seventeen patients had a solid tumor, 16 had a hematological malignancy and four recently underwent hematopoietic stem cell transplantation (HSCT) for non-oncological conditions. Twenty-eight patients presented symptoms, most often with fever, cough, rhinorrhea and asthenia. Ground-glass opacities were the most frequent radiological finding with abnormalities mostly bilateral and peripherally distributed. Twenty-four patients received chemotherapy a month prior to COVID-19 diagnosis. Most patients did not require hospitalization. Three patients required oxygen at the time of diagnosis. In total, five patients were admitted in an intensive care unit because of COVID-19 and one died from the disease. Conclusion: Children and young adults infected with SARS-CoV-2 and treated for a cancer and/or with a HSCT may be at risk for severe COVID-19 and should be closely monitored. (NCT04433871)