Kangaroos are herbivores, which means they eat only plant-based foods. Their diet mainly includes grass and other types of vegetation. Larger species, such as red and gray kangaroos, are grazers. They feed mostly on grass, much like cattle and sheep, which eat large amounts of grass in open areas.

Kangaroos have a unique digestive system that helps them process their plant-based diet. They have a chambered stomach, which functions similarly to the rumen (a specialized stomach chamber for fermenting plant material) found in ruminants such as cattle. This adaptation enables them to break down tough plant materials and extract the necessary nutrients. The fermentation process in their stomachs helps them digest cellulose, a major component of plant cell walls, which many other animals cannot digest.

Besides grass, kangaroos also eat leaves, shrubs, and tree bark—especially when grass is hard to find. This ability to adapt their diet based on availability is crucial for their survival, especially in the diverse and sometimes harsh Australian environment. Smaller species of kangaroos, such as wallabies, tend to be more selective and may focus on browsing rather than grazing.