Moxifloxacin is a widely used topical antibiotic in various bacterial infections of the eye. Its safety and efficacy have been proved by many studies. We report a case of a rare adverse effect following its use. A 10-year-old female who had presented with acute bacterial conjunctivitis in both eyes with no corneal involvement was started on preservative-free 0.5% topical moxifloxacin four times a day. The child developed a severe form of corneal toxicity in both eyes with circumcorneal congestion and corneal edema following its use. The child's visual acuity had dropped from 20/20 to 20/400 in both the eyes. Topical moxifloxacin was discontinued, following which the cornea cleared dramatically and the visual acuity became normal. This case indicates that though rare, topical moxifloxacin can cause severe keratitis and that more studies need to be conducted to evaluate its safety.