Plant-based protein powders exhibit varying flow characteristics during processing, handling, and storage. Various factors, such as physicochemical characteristics, processing conditions, and environmental conditions, determine the ease in powder flowability. Thus, it is critical to consider the flow behavior of protein powders in the design of equipment and optimization of processing conditions. This chapter provides an overview on characterization of the flow behavior of protein powders in terms flow properties accounted in Carr’s flowability and floodability indices using the Hosokawa Micron Powder Tester. Specifically, this chapter encompasses standard protocols for measuring aerated and packed bulk density, compressibility, angle of repose, angle of spatula, cohesion, angle of fall, angle of difference, dispersibility, and uniformity. This chapter also evaluates and interprets the flowability and floodability indices of select plant-based protein powders, including pea, soy, and wheat gluten.