Protein structures combining designable nutritional and functional properties are attracting great attention in the food industry. In this study, novel protein composites with shared internal structures were fabricated by co-dissolving rice proteins (RPs) and pea proteins (PPs) at pH 12 prior to a one-step neutralization. Structural and morphological characterization revealed that both unfolded protein molecules reacted at pH 12 via their secondary structures, driven by hydrophobic forces. The co-assembled structures therefore obtained considerable resistance against acid-induced refolding, affording the formation of nanoscale (∼100 nm), water-dispersible composites at pH 7. Eventually, the drawbacks of either proteins, such as the insolubility of RPs or slow digestion of PPs, were overcome due to structural alterations. Moreover, the strategy raised the level of Lys which was limiting in RPs in the same way as the level of those that were limiting in PPs such as Met and Cys-s. Based on the above results, the study would enrich the techniques of processing protein ingredients toward tailored structures and on-demand nutritional properties.