Algae are organisms rich in different metabolites, which present a wide structural diversity and biological activities. Among these metabolites, antioxidants such as carotenoids have been extensively studied. These compounds are a huge class of unsaturated tetraterpenes with many biological functions, including quenching of singlet oxygen and scavenger of other reactive species. Thus, the aim of this work was to verify the carotenoids content of three Brazilian species: Gracilaria birdae, Gracilaria dominguensis and Hypnea spinella, with economical importance, and to evaluate the antioxidant activity of their extracts. The carotenoids were extracted with hexane and analyzed by HPLC-UV, revealing the presence of some common pigments such as b-carotene, zeaxanthin and lutein in all the species analyzed. To evaluate the antioxidant activity, it was obtained extracts differing in polarity and they were tested according to their ability in suppress the DPPH radical. Moreover, it was tested the capacity of the extracts in inhibit the lipoperoxidation of linoleic acid containing micelles induced by a radical initiator. In this case, the antioxidant activity of the extracts was achieved through lipoperoxides formation, which absorbs at 234 nm, and then compared to the vitamin E equivalent antioxidant capacity. The extracts with low polarities showed higher antioxidant activity in both tests than the extracts with high polarities. G. birdae extracts exhibited the highest antioxidant activity. Although the high polarity fractions have not shown a high antioxidant capacity, further studies are needed, mainly to optimize the extraction procedure. Our results suggest that the prominent antioxidant activity of the low polarities extracts is possibly due to the presence of carotenoids.