We demonstrate an effective strategy to prepare highly stable nanoemulsions using ferrocene-modified tripeptides. Compared with traditional nanoemulsions, bioorganometallic peptide nanoemulsions are appealing for a number of reasons, including long-term and outstanding thermal stability, redox activity and biocompatibility. The formed nanoemulsions could remain stable for more than four months at room temperature, which is the highest stability reported so far for peptide and protein emulsifiers. The phase behaviour and size distribution of the emulsions could be precisely tailored by altering the temperature, solvent ratio and redox state of the ferrocene moiety. In this process, we observed a unique enthalpy-driven phase transition from nanoemulsions to hydrogels, which could be attributed to the competition between the interfacial free energy and the association energy among the self-assembling peptides. Moreover, we could impart catalytic activity to the nanoemulsions through rationally altering the sequence of the tripeptides. The structurally tunable, functional bioorganometallic nanoemulsions offer new opportunities in many areas including drug delivery, and the food and cosmetic industries.