The clinical course of SARS-CoV-2 infection (COVID-19) in children with hematologic malignancies is unclear . We describe the diagnosis, treatment and outcome of a 4-year-old boy with high-risk acute lymphoblastic leukemia and COVID-19 . Regardless of immunosuppressive induction chemotherapy his symptoms remained moderate . He received only supportive treatment . Seroconversion occurred in a similar period as in immunocompetent adults . Despite prolonged myelosuppression he did neither acquire secondary infections nor did the treatment delay caused by the infection have a measurable negative impact on the residual disease of acute lymphoblastic leukemia . Intriguingly, residual leukemia even decreased even though he did not receive any antileukemic therapy.