Urethral catheterization, a common procedure in canine patients, often compromises urinary tract defenses, leading to bacterial colonization and potential systemic infection. Despite posi-tive urine cultures, clinical signs of urinary tract infection (UTI) may be absent in catheterized dogs. This study evaluated the correlation between urinalysis results and catheter-associated UTIs in hospitalized dogs, considering prior antibiotic treatment and antibiotic resistance. Twen-ty-eight dogs at Kasetsart University Veterinary Teaching Hospital were included. Urine cul-tures and antibiotic sensitivity tests were performed on days 0, 3, and 7 and prior to catheter re-moval, with a positive urine culture defined at ≥104 CFU/mL. Instances of pyuria (>5 WBCs/HPF), hematuria (>5 RBCs/HPF), and bacteriuria were recorded. A statistical analysis showed no significant association between the urine culture results and urinalysis parameters, catheterization duration, breed, sex, neutering status, or age. Dogs with prior antibiotic treat-ments exhibited UTI-free periods after catheter placement that were longer than those previous-ly reported. A Kaplan–Meier analysis showed a probability of being UTI-free of 92.8% at 3 days, declining to 60.7% by 7 days and 53.6% by 10 days. Alarmingly, eighty percent of the isolates (12/15) were multidrug-resistant organisms (MDROs), resistant to ≥3 antimicrobials. Routine urinalysis cannot reliably predict catheter-associated UTI, and the high rate of MDROs under-scores the need for judicious antibiotic use and improved diagnostic tools.