Self-assembling biomolecular soft materials are a novel type of soft matter formed through the self-assembly process using biomolecules or biomolecular building blocks. The characteristics of bio-sourced origin and assembly driven by weak interactions endow these materials with advantages such as high biocompatibility, reversible assembly, dynamic responsiveness, and controllable microstructures. These properties offer immense potential for development in fields such as biomedicine, tissue engineering, and flexible sensing. This review offers a concise overview of the fundamental construction principles of self-assembling biomolecular soft materials and discusses three categories—nanomaterials, gel materials, and composite materials—using amino acids and peptides as examples of assembly units. The specific self-assembly molecular mechanisms, material construction strategies, and functional application scenarios of these materials are elucidated. We anticipate that the research on self-assembling soft matter biomolecular materials will evolve from exploring structural units and measuring properties to customizing multifunctional properties and integrating advanced applications. This will lead to the development of novel composite intelligent biomolecular soft matter materials, and further promoting the applications in biomedicine, organic semiconductors, and soft robotics.