Abstract Introduction Antimicrobial resistance (AMR) is an emerging crisis worldwide. If continued, it is estimated AMR could cause over 10 million deaths annually by 20501. Antifungals are critical in the treatment and prophylaxis of fungal infections, especially invasive fungal infections which can be life-threatening. The national and international antimicrobial stewardship action plan focus primarily on the use of antibacterials. Antifungals have not yet been a focus for stewardship programmes. The appropriate use and understanding surrounding antifungals remain a challenge among healthcare professionals, including pharmacists but there is scarce empirical evidence to demonstrate this problem. Aim To explore pharmacists’ understanding and use of antifungals at a tertiary hospital in England. Methods A qualitative study utilising a constructivist approach involving one-to-one online semi-structured interview based on the Critical Incident Technique2 was conducted. Pharmacists working in the tertiary hospital were purposively sampled and recruited to participate in the study. Following informed consent, participants took part in a semi-structured interview via Microsoft Teams with a researcher. Interviews explored 1) the general purpose of using antifungals and 2) system factors and decisions taken when managing a routine and unusual or challenging case using antifungals. The interviews were audio-recorded and then transcribed verbatim. Transcripts were analysed using reflexive thematic analysis3. The study was registered with the tertiary hospital where participants were recruited from. This study was registered with Oxford University Hospitals NHS Foundation Trust (ref no. 8482) and received ethical approval from the University of Reading School of Chemistry, Food and Nutritional Sciences and Pharmacy internal ethics review committee (study no: 46/2023). Results Nine participants took part in the study. Interviews took an average of 29 minutes (range 15-55 minutes). Participants worked in different specialties including oncology, haematology, paediatrics, and respiratory care. Three themes were generated through the analysis. Theme 1: Diagnosing and managing fungal infections is complex. Limited and/or lack of reliable and timely diagnostic testing makes diagnosing fungal infections difficult. Consequently, patients were sometimes prescribed empiric antifungals to avoid treatment delay. Treatment was then reviewed once test results were available. Patient-related issues such as comorbidities and drug-drug interactions contribute to complex treatment plans. Theme 2: Antifungal stewardship involved a multidisciplinary approach. Pooling together expertise amongst healthcare professionals was imperative in decision-making. Pharmacists were often key antifungal stewards and medication experts despite working with uncertainty. Theme 3: Expressed need to upskill on antifungal stewardship. Participants were aware of gaps in their experience and knowledge when managing complex fungal infections. They want to be more confident in their role. Discussion/conclusions To our knowledge, this is the first study investigating hospital pharmacists’ understanding and use of antifungals in England. Our study showed that pharmacists navigate uncertainties when using antifungals. Pharmacists were viewed as antifungal stewards and medication experts in a multidisciplinary team but pharmacists were themselves aware that they need more exposure to a wider range of scenarios to enhance their confidence. Our findings suggest a need for reliable diagnostic-driven approaches and education and training initiatives for pharmacists to steward antifungals. Our participants worked in one tertiary hospital representing the culture and work practice specific to the hospital. It would be interesting to explore experiences of pharmacists working in other hospitals.