Most people don't generally think of basil as a medicinal plant, but it has been used in traditional medicine in countries around the world and is showing promise for a variety of medical conditions. O. americanum has been used in Brazil for kidney problems and rheumatism and in Sudan and India for skin parasites.

The leaves and roots of O. kilimandscharicum have been used to treat colds and stomach complaints in Africa. O. basilicum has been used in traditional Chinese medicine for kidney problems, gum ulcers and as a hemostyptic in childbirth and for problems as diverse as earache, rheumatoid arthritis, anorexia, skin conditions, menstrual irregularities, and malaria in India.

O. basilicum alone has over fifty medicinal activities, from analgesic to vermifuge, and is reportedly used to treat over 100 conditions, including acne, fevers, headaches and fungal infections. Many of these uses are folkloric and have not been verified in scientific studies, but others have begun being tested in controlled animal experiments. A recent animal study of O. suave (O. gratissimum) found anti-ulcer effects, and a study of O. canum (O. americanum) suggests that it can lower blood sugar levels and aid "insulin release" in rats. O. tenuiflorum has demonstrated anti-inflammatory effects in animal studies.

Several basil species have antimicrobial and antifungal properties. O. basilicum and O. gratissimum are reported to be antimicrobial/antibacterial and antifungal, and the oils of Ocimum xcitiodorum 'Citriodorum' and Ocimum kilimandscharicum are antifungal.