Bacterial keratitis is a serious ocular infectious disease that can threaten vision. The disease generally progresses rapidly and can lead to corneal scar, stromal abscess formation, perforation, and dissemination to adjacent tissues if not treated properly. Recent studies showed that corneal collagen crosslinking (CCC) using ultraviolet-A/riboflavin is effective in the treatment of bacterial keratitis refractory to topical antibiotic treatment. In addition to being bactericidal, CCC also decreases risk of perforation by strengthening the corneal collagen structure. Herein, we report a male patient with Streptococcus pneumonia keratitis 6 months after a keratoplasty procedure, which did not respond to fortified topical antibiotic therapy and was treated successfully with riboflavin/ultraviolet-A CCC. His pain decreased remarkably in a few days. The corneal epithelial defect healed and infiltration regressed within 2 weeks after CCC. His vision improved significantly from hand movement to 20/400. CCC might be used as adjuvant treatment in bacterial keratitis refractory to medical treatment.