Rice protein concentrate (RPC) has raised interest in food industries due to its nutritional value and nutraceutical properties. However, RPC powder presents fine particles (D50 = 54.2 µm) with moderate flowability and low wettability in liquids, limiting its use as a food ingredient or dietary supplement. The production of porous granules with high wettability, called instant powders, is performed by agglomeration process. Therefore, the agglomeration process represents an efficient way to improve the quality of the RPC powder. Grape pulp can be a potential binder for the agglomeration of RPC since it is rich in anthocyanins, that are associated with human health benefits. This study aimed to establish the optimal condition to produce an instant and nutritional food powder by fluidized bed agglomeration of RPC using grape pulp as binder. The influence of binder flow rate (1.5-2.5 mL.min-1) and fluidizing air temperature (65-85 °C) upon the process yield, median particle size and anthocyanins content was examined using a complete factorial design. Moreover, the effect of operating conditions on particle size evolution was evaluated by a spatial filter velocimetry probe. Surface response analysis pointed out the optimal operating condition (76 °C and 1.8 mL.min-1) that provided large granules (D50 = 302.8 µm) with anthocyanins incorporation (11.79 mg/100g) and high process yield (71.1%). This condition afforded an instant powder with low moisture content (3.33%), reduced wetting time (4.1 s) and very good flowability. The results suggest that grape pulp can be of special value for application as a binder in agglomeration of RPC. In-line particle size data provided a better understanding of both growth and breakage of the particles during the process, which were strongly influenced by the binder flow rate and air temperature. The instant powder produced presents a high potential to be used as an ingredient in food formulations.