As an indicator of sustainable development, the ecological footprint has been successful in providing a basis for discussing the environmental impacts of human consumption. Humans are at the origin of numerous pollutant activities on Earth and are the primary drivers of climate change. However, very little research has been conducted on the environmental impacts of animals, especially companion animals. Often regarded as friends or family members by their owners, companion animals need significant amounts of food in order to sustain their daily energy requirement. The ecological paw print (EPP) could therefore serve as a useful indicator for assessing the impacts of companion animals on the environment. In the present article, we explain the environmental impact of companion dogs and cats by quantifying their dietary EPP and greenhouse gas (GHG) emissions according to primary data we collected in China, the Netherlands, and Japan and discuss how to reduce companion dietary EPP and GHG emissions in order to understand the sustainability of the relationship between companion animals and the environment.