Green Oats (Avena sativa L.), also known as “Avena Sativa”, are a type of cereal mainly grown in North America and Europe. Green Oats are highly effective for targeting a broad spectrum of diseases. The beneficial effects are largely due to various bioactive phytochemicals, such as β-glucan, dietary fiber, and phenolic compounds, especially avenanthramides. These nutrients help reduce oxidative damage, inflammation, and tumor progression, and promote cognitive health. This review highlights the nutraceuticals and health-promoting values of green oat and its extracts, focusing on their compositions, biological effects, and underlying molecular mechanisms.