Hybrid systems combining animal and plant proteins are promising for developing sustainable, high-protein foods. However, structural incompatibility between proteins like casein and pea protein hinders the formation of stable systems such as gels. This study explores pH-shifting (alkalization at pH 12 followed by neutralization) as an innovative strategy to improve pea protein functionality and compatibility in hybrid gels. Modified pea protein showed increased solubility, reduced particle size, higher zeta potential, and decreased intrinsic fluorescence intensity, indicating conformational changes and exposure of buried tryptophan residues. These structural changes influenced gel behavior depending on the protein ratio (casein/pea—80:20, 50:50, 20:80). Gels with higher pea content showed increased hardness and water-holding capacity, while in casein-rich gels, hardness decreased, likely due to altered protein–protein interactions. This is the first study to systematically apply pH-shifting to enhance the compatibility between pea protein and casein in high-protein gels, integrating structural and functional analyses. The results demonstrate the potential of pH-shifting as a sustainable and effective approach for improving plant protein performance in hybrid formulations.