The production of bone-, dentine- and enamel-like biomaterials for the engineering of mineralized (hard) tissues is a high-priority in regenerative medicine and dentistry. An emerging treatment approach involves the use of short biomimetic peptides that self-assemble to form micrometer-long nanofibrils with well defined surface chemistry and periodicity that display specific arrays of functional groups capable of mineral nucleation. The fibrils also give rise to dynamically stable 3D scaffold gels for the potential control of crystal disposition and growth. Peptides can also be injected in their monomeric fluid state, with subsequent self-assembly and gelation in situ triggered by physiological conditions. In this way, they can infiltrate and self-assemble within irregular or microscopic cavities, for restorative treatment of bone defects, dentinal hypersensitivity or dental decay. Cell adhesion and proliferation is also supported by these scaffolds, offering further advantages for applications in hard tissue engineering. These self-assembling matrices also provide well defined model systems that can contribute greatly to the elucidation of the biological mechanisms of protein-mediated biomineralization.