A 19-year-old woman presented with a 3-day history of pain, redness, and diminution of vision occurring one day after collagen crosslinking (CXL) with riboflavin and ultraviolet-A had been performed for keratoconus in the right eye. On presentation, severe keratitis with a 7.0mm x 6.0mm central infiltrate was present. Culture results from the patient's contact lens and corneal scrapings were positive for Pseudomonas aeruginosa. Keratitis can occur following CXL because of the presence of an epithelial defect, use of a soft bandage contact lens, and topical corticosteroids in the immediate postoperative period, and patients should be counseled about it.