Antimicrobial stewardship is getting increasing attention in veterinary medicine and assessment of antimicrobial use practices is a core component of stewardship activities. A retrospective review of antimicrobial prescriptions for dogs diagnosed with infectious urinary tract disease in veterinary practices in the United States and Canada was performed to evaluate antimicrobial prescribing. A total of 7803 antimicrobial prescriptions from 7387 dogs were evaluated; 7127 dogs from 673 clinics from the US and 260 dogs from 50 clinics in Canada. The main clinical concerns were acute cystitis (n=6582), recurrent cystitis (n=428) and pyelonephritis (n=326). Amoxicillin/clavulanic acid (2702, 41%), cefpodoxime (1024, 16%) and amoxicillin (874, 13%) were the most commonly prescribed antimicrobials for acute cystitis. The median duration was 12d (range 3-60 days, interquartile range (IQR) 4 days). There was a significant difference in duration between 2016 and 2018, and 2016 and 2018 (both P< 0.001), with lower duration in 2018. 55% (3634) dogs were treated with a recommended first line drug, rising from 52% (736/1410) in 2016, 53% (1348/2536) in 2017 and 59% (1550/2636) in 2018 (P< 0.0001). There were significant differences in prescription patterns and overall use of ‘highest priority critically important antimicrobials’ between Canada and the US, and between different US regions. Amoxicillin/clavulanic acid (146, 33%), marbofloxacin (95, 21%) and cefpodoxime (65, 14%) were most commonly used for recurrent cystitis, with a median duration of 14d (range 3-77, IQR 10.5). Amoxicillin/clavulanic acid (86, 26%), marbofloxacin (56, 17%) and enrofloxacin (36, 11%) were most commonly prescribed for pyelonephritis; however, 91 (28%) dogs received two antimicrobials and two (0.6%) three antimicrobials. The median duration of treatment was 14d (range 3-77d, IQR 11d). Fluoroquinolones were prescribed significantly more often (P< 0.0001) to dogs with pyelonephritis compared to dogs with acute cystitis, while first (P=0.018) and third generation cephalosporins (P=0.009) and penicillins (P=0.0007) were more commonly prescribed to acute cystitis cases Decreases in duration and increased use of recommended first line antimicrobials over the study period were encouraging but room for interventions to optimize antimicrobial use remains.