Vegan dog food is less damaging to the environment, and to the welfare of animals processed into pet foods. But – are vegan diets good for dogs? To test this, we collected data on 2,536 dogs fed a conventional meat (1,370 = 54%), raw meat (830 = 33%) or vegan (336 = 13%) diet for at least one year. We examined seven general indicators of ill health: unusual numbers of veterinary visits, medication use, progression onto a therapeutic diet after initial maintenance on a vegan or meat-based diet, guardian opinion and predicted veterinary assessment of health status, percentage of unwell dogs and number of health disorders per unwell dog. We also considered the prevalence of 22 of the most common canine health disorders. Percentages of dogs in each dietary group considered to have suffered from health disorders were 49% (conventional meat), 43% (raw meat) and 36% (vegan). The pooled evidence from this very large-scale study, along with others in this field, indicates that the healthiest and least hazardous dietary choices for dogs, are nutritionally sound vegan diets.