Anthocyanin stability and antioxidant activity of powdered açai juice was evaluated throughout 120 days. Powders were produced by spray drying using four types of carrier agents: maltodextrin 10DE, maltodextrin 20DE, gum Arabic and tapioca starch. Samples were stored at different temperatures (25 and 35 _C) and water activities (0.328 and 0.529), in order to verify the effect of these conditions on anthocyanin degradation and antioxidant activity reduction. Anthocyanin degradation exhibited two first-order kinetics: the first one, with higher reaction rate constant, up to 45-60 days of storage, and the second one, after this period, with lower degradation rate. Both temperature and water activity negatively affected anthocyanin stability. Antioxidant activity also decreased with increasing water activity, but was higher for the powders stored at 35 _C. Maltodextrin 10DE was the carrier agent that showed the best pigment protection and the highest antioxidant activity, for all the conditions studied. (Résumé d'auteur)