Caged xanthones, characterized by a unique 4-oxa-tricyclo[4.3.1.0(3,7)]dec-2-one scaffold, are a special class of bioactive components mainly derived from the Garcinia genus (Guttiferae family). Around 100 compounds from this family have been reported to date and most of them have potent antitumor activity, with gambogic acid being the best representative. During the past decades, inspired by the unusual caged skeleton and remarkable bioactivity, scientists from various fields have shown increasing interest on these promising natural products. In this review, the plant resources, structural characteristics, total synthesis, biological activity and mechanisms of action, structure activity relationship, and anticancer drug development of these caged xanthones are described.