A healthy 28-year-old man developed a slowly progressive corneal ulcer 21 months after an episode of corneal trauma. Acid-fast bacilli were identified in corneal scrapings, and the causative organism was identified as Mycobacterium avium-intracellulare. Medical treatment with topical amikacin and oral rifampin was ineffective, and a therapeutic penetrating keratoplasty was necessary to cure the infection. To the best of our knowledge, this is only the second reported case of a corneal infection caused by a slow-growing nontuberculous mycobacterium (Runyon groups I, II, and III) and the first caused by M. avium-intracellulare. Slowly growing nontuberculous mycobacteria should be considered among those organisms that cause corneal infection, especially in cases characterized by a protracted course and lack of response to conventional antimicrobial therapy.