The therapeutic potential of antimicrobial peptides (AMPs) has been evaluated in many infectious diseases. However, the topical application of AMPs for ocular bacterial infection has not been well investigated. The AMP OH-CATH30, which was identified in the king cobra, exhibits potent antimicrobial activity. In this study, we investigated the therapeutic potential of OH-CATH30 for Pseudomonas aeruginosa keratitis. Ten isolates of P. aeruginosa from individuals with keratitis were susceptible to OH-CATH30 but not to cefoperazone, ciprofloxacin, gentamicin, and levofloxacin. The microdilution checkerboard assay showed that OH-CATH30 exhibited synergistic activity with ciprofloxacin and levofloxacin against antibiotic-resistant P. aeruginosa. Meanwhile, P. aeruginosa did not develop resistance to OH-CATH30, even after exposure at 0.5x the MIC for up to 25 subcultures. Furthermore, treatment with OH-CATH30, alone or in combination with levofloxacin, significantly improved the clinical outcomes of rabbit keratitis induced by antibiotic-resistant P. aeruginosa. Taken together, our data indicate that the topical application of OH-CATH30 is efficacious against drug-resistant P. aeruginosa keratitis. In addition, our study highlights the potential application of AMPs in treating ocular bacterial infections.