Background: The development of Nocardia keratitis in a patient with human immunodeficiency virus infection is rare, and we could find no cases reported in the literature. Case: A 48-year-old woman who had human immunodeficiency virus infection presented with decreased visual acuity, redness, and irritation in the right eye. Observations: Initially, the diagnosis was fungal keratitis, and she was treated with 0.3% amphotericin B eye drops and oral fluconazole for 1 month without improvement. Then, all former drugs were discontinued, and a corneal scraping was carried out. The culture result disclosed Nocardia asteroides, and after treatment with 10% sulfacetamide eye drops and oral trimethoprim-sulfamethoxazole, the keratitis subsided dramatically. Conclusions: The treatment result for Nocardia keratitis in a human immunodeficiency virus patient was favorable after intensive use of 10% sulfacetamide eyedrops. Nocardia keratitis should be kept in mind as a possible causative organism when antifungal therapy fails in a keratitis case. © Japanese Ophthalmological Society 2004.