Aspergillus fumigatus is recognized as the most common causative agent of aspergillosis, a disease whose severity depends on the host’s immune status. In immunocompromised individuals, this infection can lead to invasive aspergillosis, a life-threatening condition. A. fumigatus presents a challenge due to increasing resistance to antifungal therapies, and its ability to adapt to various stress conditions, especially those related to the immune system. The yap1 gene in A. fumigatus is known to be involved in oxidative stress response. In this study, we aimed to investigate its function under different stress conditions, including oxidative, osmotic, cell wall, and heavy metal stress. The results revealed that Yap1 is essential for oxidative stress response in A. fumigatus but does not significantly contribute to osmotic, cell wall, and heavy metal stress responses.