Entirely plant-based diets for dogs are increasing in popularity. However, research on the impact of these diets on gastrointestinal health is limited. The research presented in this thesis included three studies: a apparent total-tract nutrient digestibility trial, a fecal microbiome trial, and a fecal metabolome trial to compare an experimental plant-based diet to a conventional animal-based diet in 61 client-owned healthy adult dogs.The plant-based diet was found to have comparable crude protein, crude fat, and dry matter ATTD to the dogs fed the animal-based diet. The plant-based diets showed the potential to change the canine fecal microbiota, but these changes were distinct from those reported in human literature. Furthermore, the plant-based diet increased fecal metabolites mainly associated with carbohydrate digestion, this supporting previous research into dogs’ adaptation to digest and metabolize carbohydrates. The findings of this research provide the basis of future investigation into the impacts of plant-based diets on canine health.