The management of heat-related illness (HRI) in dogs has received limited attention in the veterinary literature, especially regarding effective cooling methods. Guidelines published in 2016 for prehospital management of dogs with HRI advised “cool first, transport second”, and recommended using cold-water immersion and evaporative cooling (water application with air movement) as the optimal approaches to reduce the patient’s temperature. The current retrospective cross-sectional observation study analysed electronic patient records from the VetCompass programme to describe the cooling methods used in dogs with HRI presented to primary care veterinary practices during 2016–2018. Of 623 HRI events identified, 341 (54.74%, 95% CI 50.81–58.60%) included information on cooling in their clinical record. Of these, 74/341 (21.70%, 95% CI 17.65–26.38%) were cooled prior to transport for veterinary care. Overall, 23.97% (95% CI 19.24–29.44%) were cooled using one of the two recommended cooling methods, whilst the most common cooling method recorded was the application of wet towels (51.31%, 95% CI 45.34–57.24%). Canine cooling guidance and messaging in both the public and veterinary sectors requires urgent review to ensure that the most effective cooling methods are promoted because delays to canine temperature reduction worsen patient outcomes.