The commercial production of mushrooms is often carried out in indoor areas and controlled environments with intense labor performed throughout the year. Indoor cultivation can lead to allergic symptoms, such as extrinsic allergic alveolitis, also known as hypersensitivity pneumonitis, in workers. A 23-yearold male patient's symptoms emerged after beginning to work in mushroom cultivation. The patient was admitted to the clinic with complaints of chills, fever, joint pain, and a skin rash. Based on his medical history and a physical and radiographical examination, the patient was diagnosed as hypersensitivity pneumonitis and medical therapy was initiated. The patient's symptoms disappeared within a few days and he was discharged at the end of the first week. Given the difficulties in the diagnosis of disease, the patient's professional history should always be kept in mind as well as medical history, physical examination, and radiographic evaluation.