This work aims to elucidate the particle growth mechanism during agglomeration using a bottom-spray fluidized bed process to produce technical catalysts. The influences of the fundamental operating parameters of the granulation process were investigated through (i) experiments in a newly designed small-scale bottom-spray fluidized bed reactor, (ii) morphological characterization of the catalytic particles produced, (iii) dimensionless number analysis, and (iv) principal component analysis. These results could define the growth stage as dust formation, seed formation, agglomeration, and dust integration or layering. The particle growth mechanism results from the complex interplay of several effects and forces (mass transfer, viscous force, inertial force, surface tension, and gravity), and the prevailing growth stage can be linked with the Weber (We) and capillary (Ca) numbers (i.e., low values of We = 5.7 and Ca = 1.4 leads to layering growth and high values of We = 19.1 and Ca = 7.1 results in dust formation).