Background and Objectives: Due to immune suppression, patients with hematological malignancies are at a high risk of invasive fungal disease (IFD) during chemotherapy. For patients with myeloid tumors, antifungal prophylaxis is generally recognized. However, there are evident interactions between agents used in acute lymphoblastic leukemia (ALL) remission-induction and antifungal agents, resulting in most clinical trials excluding ALL patients. The need for primary antifungal prophylaxis in ALL patients during chemotherapy is still under debate. This study analyzed the efficacy of primary antifungal prophylaxis (PAP) and the incidence of IFD during the first remission induction in the PDT-ALL-2016 cohort, as well as evaluated the impact of PAP on the outcomes of ALL patients. Methods: The PDT-ALL-2016 cohort consists of 408 newly diagnosed ALL patients aged ≥ 14 years, treated between January 2016 and December 2021. All patients were treated using the GRAALL-2003 backbone, a pediatric-like regimen. This study included 280 patients, with a total of 128 exclusions. Excluded patients consisted of 103 individuals who received initial induction treatment in other hospitals, 12 individuals who died without IFD during the induction period, 9 individuals who experienced fungal infection before induction treatment, 2 individuals who did not complete induction remission treatment and were discharged, and 2 individuals who had lost their cases. PAP was defined as the administration of any systemic antifungal agent for two or more consecutive days to a patient without any evidence or history of IFD during the neutropenic period. The diagnosis of IFD was based on the European Organization for Research and Treatment of Cancer/Mycosis Study Group criteria. Results: Among the 280 patients, 232 received PAP, with caspofungin (n=104), voriconazole (n=59), micafungin (n=44), and others being used as prophylaxis. The baseline characteristics of patients who did or did not receive PAP were similar, except for the age difference (prophylaxis group median age 28.7 versus without prophylaxis group 23.0, P<0.01). In the cohort, 11 proven/probable and 21 possible IFD cases were identified. The incidence of IFD in patients who did or did not receive PAP was 8.6% and 25.0%, respectively. The cumulative incidence of IFD was significantly lower in patients receiving PAP compared to those who did not (HR 0.3, 95% CI 0.1-0.6; P=0.001). In the cohort, the infections of IFD negatively affected overall survival (HR 1.6, 95% CI 0.9-2.7, P=0.093). Conclusions: Our study demonstrates, in a real-life setting, that IFD is a poor prognostic factor for adult ALL and that PAP significantly reduces the incidence of IFD during induction chemotherapy, thereby improving patient survival. Furthermore, compared to published studies (4.3%-18.3%), the incidence of IFD in the prophylaxis group within our cohort is relatively lower. This research was supported by the National Natural Science Foundation of China(NFSC82170163, 81970147), Clinical Study of Nanfang Hospital(LC2016ZD009/2019CR012).