We report a case of bacterial keratitis 3 days after corneal crosslinking for keratoconus. The patient complained of increasing pain and redness combined with blurred vision in the treated eye starting on the first postoperative day. Clinical examination showed multiple stromal infiltrations and moderate anterior chamber inflammation. Corneal scraping revealed an Escherichia coli infection, which was successfully treated with fortified tobramycin and cephazolin eyedrops for several weeks. This is the first report of a case of rare postoperative complication resulted in an avascularized corneal scar and permanent reduction of the visual acuity.