Background <p>Fungal keratitis can develop after plant injury or after prolonged glucocorticoid use. Typical manifestations include corneal infiltrates, satellite lesions, plaques, and an immune ring. Some cases exhibit atypical signs, requiring reliance on etiological examination. Notably, fungi previously deemed nonpathogenic to humans can cause keratitis with rare clinical manifestations. This report details the clinical signs and successful treatment outcomes of keratitis caused by <i>Phaeoisaria sp.</i></p> Case presentation <p>A 51-year-old man visited the ophthalmology clinic with ongoing eye pain and a history of corneal iron foreign body removal two months earlier. Examination revealed a brownish ulcer with clear borders, swelling, and redness, indicating the presence of rust. Although the initial cultures were negative, a rare fungus called <i>Phaeoisaria sp.</i> was eventually identified as causative agent. The patient completed six weeks of antifungal treatment and showed no signs of recurrence at the 7-month follow-up visit.</p> Conclusions <p>Patients with a history of corneal foreign bodies should also be informed of the possibility of atypical corneal fungal infection.</p>