Background: Childhood acute lymphoblastic leukaemia (ALL) cure rates have improved, but invasive mould disease (IMD) remains a life-threatening complication. Here, we evaluate the epidemiology, clinical presentation, treatment and outcome of IMD in paediatric patients with ALL. Methods: Patients (1–18 years) treated according to the Dutch Childhood Oncology Group (DCOG) ALL-11 protocol from 2012–2021 were analysed for probable and proven IMD. Data was extracted from the Dutch national registry and the electronic health care system. Results: Among 643 patients with ALL, 47 (7.3%) were diagnosed with a probable (n = 29) or proven (n = 18) IMD. Aspergillosis was diagnosed in 42 (89%) patients. Forty-one episodes (87%) occurred during the induction (n = 20) and first consolidation (n = 21) course. The median age at ALL diagnosis was 5 years [IQR 3–10] in the overall group versus 14 years [IQR 7–16] in the IMD group. Two-third of the patients did not receive mould-active prophylaxis. The most prevalent clinical symptoms at presentation were persistent fever and respiratory symptoms. The lungs were the most common site of infection with involvement in 44 (94%) patients, followed by the CNS in 16 (34%) patients. The 6-week and 12-week mortality rate after IMD diagnosis was 10.6% and 14.9%, respectively. Discussion and conclusion: In our paediatric cohort a notable incidence of probable and proven IMD was observed during the early stages of treatment. Remarkable is the high frequency of CNS involvement. These findings highlight the importance of effective prophylactic strategies and warrant early brain imaging