OBJECTIVE To assess and compare the efficacy and safety of posaconazole with fluconazole for the prevention of invasive fungal infections in children who were undergoing induction therapy for acute lymphoblastic leukemia (ALL). To develop an approach to predict invasive fungal infections in ALL patients who accepted posaconazole prophylaxis. METHODS This was a single-center, retrospective cohort study of patients with newly diagnosed ALL, comparing invasive fungal infections in patients who received no prophylaxis, posaconazole prophylaxis, or fluconazole prophylaxis during induction therapy. A propensity score-weighted logistic regression model was used to adjust for confounders. Hepatotoxicity was assessed according to the Common Terminology Criteria for Adverse Events (CTCAE) criteria. RESULTS Out of the 155 ALL patients, 60 received no prophylaxis, 70 received posaconazole prophylaxis, and 25 received fluconazole prophylaxis. Posaconazole prophylaxis reduced the odds of invasive fungal infections by > 60%, prolonged infection-free survival significantly, and did not increase the risk of hepatotoxicity. Additionally, we found that the combination of age at diagnosis, clinically documented bacterial infection in the first 15 days of induction therapy, and absolute neutrophil count (ANC) curve enabled significant prediction of the susceptibility to infections after receiving posaconazole prophylaxis. CONCLUSIONS Our findings supported using targeted prophylaxis with posaconazole in ALL children undergoing induction chemotherapy. Age, clinically documented bacterial infection and ANC are important predictors of invasive fungal infections in patients with posaconazole prophylaxis.