The efficient utilization of soybean by-products, such as soybean hull and wet okara, has significant potential in enhancing their economic value in the food industry. In this study, extruded soybean by-products (ESBP) particles were processed using dynamic high-pressure microfluidization (DHPM) to produce microfluidized ESBP (MESBP) particles. The physicochemical properties and structural characteristics of MESBP particles and the emulsions they stabilize were comprehensively evaluated. The results showed that DHPM treatment did not alter the chemical bonds and crystalline structure of MESBP particles but induced a rougher and more porous microstructure. While ESBP particles alone were unable to form stable emulsions, MESBP particles exhibited improved emulsifying properties with increasing DHPM intensity, including smaller particle sizes, higher absolute ζ-potential values, and larger contact angles. Correspondingly, the droplet sizes of emulsions stabilized by MESBP particles decreased, while their absolute ζ-potential, apparent viscosity, viscoelastic (G') and viscous (G′') moduli increased with increasing DHPM intensity. Emulsions stabilized by MESBP particles treated at high DHPM intensity demonstrated superior storage and physical stability, attributed to the formation of a gel-like network structure via strong particle adsorption at the oil–water interface. The findings present a promising strategy for valorizing soybean by-products as effective particulate emulsifiers, thereby broadening their application in the food sector.