Mentha aquatica L. (water mint) is known as a medicinal plant that has many novel compositions. The phenolic compounds and essential oils in Mentha aquatica L. played an important role in many types of diseases treatments such as flatulence, anorexia, indigestion, ulcerative colitis, etc. However, there are still little data concerning these compounds and their functions. The aim of this study was to review the biological activities, phenolic compounds, and essential oils in Mentha aquatica L.