Proteus mirabilis is a major bacterium responsible for catheter-associated urinary tract infections (CAUTIs). Urease enzyme has a great role in the pathogenesis of Proteus mirabilis. Using urease, Proteus mirabilis can decompose urea to produce ammonia that increases urine pH and enhances crystal precipitation and crystalline biofilm formation. This leads to catheter blockage and pyelonephritis, respectively. Urease inhibitors are of great value in controlling this problem. Diclofenac sodium and ketorolac tromethamine, with their metal chelating activities, can inactivate urease by chelation of nickel ion in the active site of urease. This study investigated the ability of diclofenac sodium and ketorolac tromethamine to inhibit urease activity in Proteus mirabilis and crystalline biofilm formation. Diclofenac sodium and ketorolac tromethamine showed comparable activities against urease in cell lysates and whole cultures, with subsequent inhibition of pH increase and crystal formation in artificial urine. Diclofenac sodium showed higher biofilm inhibition and downregulation of urease genes ureR and ureC in RT-qPCR. The docking study showed the ability of both drugs to bind to urease enzyme and to chelate nickel ions in the active site of urease, suggesting that nickel chelation is the mode of inhibition of urease enzyme. In conclusion, diclofenac sodium and ketorolac tromethamine are two urease inhibitors that may be useful in treating Proteus mirabilis CAUTI.