Ugni molinae Turcz is a Chilean native plant widely distributed in Central South Chile as well as in Juan Fernandez Archipelago. Its fruits are consumed fresh because of its organoleptic properties. Given the importance of the chemical compounds identified from U. molinae, it becomes important to know if there are variations in the chemical content and biological activity among populations growing geographically separated, as well as in different habitats, such as those populations that grow in Continental Chile and in Juan Fernandez Archipelago. The aim of this work was to assess the chemical composition and the antioxidant capacity of extracts from populations of U. molinae that grow in Continental Chile and in Juan Fernandez Archipelago. Composition of chemical compounds was determined by chromatographic methods (HPLC-ESI-MS). Antioxidant capacity was assessed by means of unspecific methods (DPPH and ABTS) and stabilization of the hydroxyl radical. Differences are observed in the chemical composition among continental and insular (Juan Fernandez Archipelago) populations of U. molinae. The latter presents greater content and variety of phenolic and triterpenic glycosides of oleanone type. These populations exert greater antioxidant capacity, probably due to the insular geoclimatic conditions.