The antioxidant activity and antimicrobial property of phenolic extracts from acerola (Malpighia emarginata DC) fruit were assessed. The contribution of ascorbic acid and phenolic compounds in the total antioxidant capacity of the extracts was also evaluated. The extracts showed high total phenolic values and possessed high antioxidant activity as expressed by 2,2′-diphenylpicrylhydrazyl (DPPH) and oxygen radical absorbance capacity assays (ORAC). The ascorbic acid content ranged from 405 to 1744 mg/100 g of fruit on a fresh weight basis. The antioxidant capacity of the phenolic fractions was in the following order: anthocyanins<phenolic acids<flavonoids. The phenolic fractions contributed 7.1–36.5% of the antioxidant activity expressed by ORAC, whereas the contribution of ascorbic accounted for 18–39% of the total activity. Selected extracts from the flavonoids fraction showed some activity against Staphylococcus aureus.