Obesity in humans is a growing global problem and is one of the greatest public health challenges we face today. Most researchers agree that, as in humans, the incidence in the companion animal population is also increasing. The aim of this study was to evaluate the risk factors contributing to canine obesity in a region with a high rate of human obesity (Canary Islands, Spain), co-occurrence of obesogenic risk factors, and a canine population with a high percentage of unneutered dogs. We have focused on owner risk factors that promote obesity in humans, such as weight, lifestyle, nutritional habits, and low physical activity, among others. Thus, the human–animal interaction relationship that contributes to human obesity and influences canine obesity has been studied. A multicentre cross-sectional analytical study of 198 pairs of dogs from urban households and their owners was used. A multivariable logistic regression study was completed to analyse owner characteristics variables associated with canine obesity. This transdisciplinary study was conducted with physicians and veterinarians using a “One Health” approach. Our results suggest that, in a region of high obesogenic risk, obese/overweight dogs are primarily female, older than 6 years, and neutered. Being an overweight dog owner was found to be the most important factor in the occurrence of obesity in dogs. Owners of overweight dogs were mainly females, older than 40 years, who did not engage in any physical activity. A strong correlation has been found between dog owners with low levels of education and obesity in their dogs. We suggest that veterinarians should develop and design strategies to encourage pet owners to engage in physical activity with their dogs for the benefit of both.