Nowadays, there is a demand for products with good nutritional, technological and sensory characteristics. In this context, vegetable protein isolates, as pea protein, has been studied as a substitute to the soy protein, since it has higher levels of essential amino acids and vitamins. These powders are obtained commonly by spray drying that can modify the protein structure and that produces fine particles. So, to improve physicochemical properties, other processes, as agglomeration in fluidizing bed, could be used. The aim of this work was to study the influence of binder solutions characteristics on particle growth kinetics using an in-line particle size monitoring by spatial filter velocimetry. Two different acacia gum solutions (0.7 and 20.0 % w/w) were used as liquid binder. The operating conditions used were drying air temperature of 75 °C and binder flow rate of 3.0 mL/min. Atomization air pressure and atomization nozzle height were kept constant at 7.0 psi and 0.3 m, respectively. Fluid bed agglomeration was a useful method to produce instant pea protein concentrate powder under the operating conditions studied. This process produced larger particles, free-flow improved and shorter wetting time. The binder solution with higher concentration and more viscous provided a more pronounced particle growth and higher process yield. The in-line particle size monitoring was useful to observe the particle growth kinetics and the operating conditions influence on the growth kinetics and particle growth rate in fluidized bed agglomeration. It also was possible to observe that the particle growth rate oscillated during the process showing that the particle size growth results from a positive balance between agglomeration and break.