Acai is a palm widely distributed in the Amazon estuary floodplains. The edible pulp of acai fruits is commonly macerated with water to produce a thick, purple beverage of creamy texture, oily appearance, and characteristic flavor. Depending on the Brazilian region, the acai based-product is prepared adding sugar and guarana extract, but their ideal proportions have never been determined in order to optimize consumers’ sensory acceptance. This research investigated these concentrations using response surface methodology (RSM) based on a five-level, two variable central composite rotatable design (CCRD). Dependent variable was consumer acceptance (flavor, texture and overall liking) and results were analyzed by multivariate regressions. Analyses of Variance (ANOVAs) showed significant models – F-test values (29.3 for flavor, for texture 37.8 and 30.4 for overall liking) higher than the critical value of 4.35 (d.f. = 3; p < 0.05; R² of 0.926 for flavor, 0.942 for texture and 0.929 for overall liking). Acceptance models are presented (significant parameters). Results showed that guarana extract has a stronger influence (negative) on acceptance compared to sugar (positive), both not on optimal conditions yet. Therefore, more studies are needed in order to optimize acai acceptance.