Purpose: To report a case of contact lens-related infectious keratitis caused by three different bacterial species.Case summary: A 40-year-old man presented with pain and redness in his left eye. His best-corrected visual acuity (BCVA) in the affected eye was 20/25. Slit-lamp examination revealed a 3 × 3 mm corneal epithelial defect with infiltration located 1 mm inferior to the pupil. Following admission, a microbial culture test was performed, and empirical antibiotic therapy was initiated. On the fourth day, <i>Pseudomonas aeruginosa</i> was isolated from the corneal sample and the contact lens, while <i>Serratia marcescens</i> and <i>Stenotrophomonas maltophilia</i> were isolated from the contact lens case. Based on the results of the antibiotic susceptibility tests, 0.5% moxifloxacin, fortified amikacin, and ceftazidime were administered topically and intravenously. The corneal epithelial defect reduced to 1 × 1 mm by the eleventh day of admission. After two months, BCVA improved to 20/20 with no remaining corneal epithelial defect, although an inactive corneal opacity persisted at the previous ulcer site.Conclusions: Contact lens wear can be associated with polymicrobial keratitis involving three distinct Gram-negative bacteria, which may present greater treatment challenges compared to monomicrobial keratitis. Microbial culture testing of the contact lens, its case, and corneal scrapings is essential for identifying the causative organisms and selecting appropriate antibiotic therapy.