Legume cooking water (CW) is a food by-product with the potential of becoming a plant-based egg white replacement; however, limited research has been performed on processes to propel its industrialisation. Consequently, this study assessed the impact of concentration methods (thin-film evaporation; cryoconcentration [CC]; and stove-top boiling [BL]) on the composition and characteristics of spray-dried CW powders. CW was concentrated from 6.8 to 22 °Brix. Subsequent analyses showed that the powder characteristics were an outcome of their particle size and composition. CC powders with 18.56 ± 0.85% protein and D₅₀ = 0.14 ± 0.01 μm presented the lowest-performing functionality. Conversely, BL powders (25.13 ± 0.50% protein and D₅₀ = 3.70 ± 0.47 μm) displayed enhanced emulsification and foaming. Hence, the properties of CW improved with thermal concentration. These results lay the ground for selecting and optimising a concentration procedure aiming to industrialise the production of CW.