Bacterial coaggregation is a critical process in multispecies biofilm formation, driven by specific molecular interactions that facilitate the adhesion and aggregation of bacterial cells. These interactions are essential for the development and persistence of complex microbial communities. This review provides a comprehensive analysis of the roles of the proteosurfaceome and exoproteome in bacterial coaggregation. The proteosurfaceome, comprising surface-bound molecules such as adhesins, drives species-specific interactions crucial for partner recognition and adhesion. In parallel, the exoproteome, particularly extracellular polymeric substances (EPS), enhances aggregate stability by reinforcing structural integrity and facilitating intercellular communication, although its direct role in coaggregation remains to be fully clarified. By integrating these perspectives, this review aims to elucidate how the proteosurfaceome and exoproteome influence bacterial coaggregation, offering insights into their combined impact on microbial community structure and function. Furthermore, we highlight existing knowledge gaps and propose directions for future research.