Chemical straightening of curly human hair fibres involves the use of strong reducing agents at alkaline pH. Human hair is made of keratin, and the fixation of fibre shape involves the reduction and reformation of new disulphide bonds between keratin molecules. Here, we propose an alternative and green methodology using keratin peptide sequences (10–13 residues) derived from the human genome. In a previous study, we analysed 1235 cysteine-containing peptides encoded by all human genes of hair keratin and keratin-associated proteins. These peptide fragments have been designed by nature to interact with keratin. Here we tested eight peptides, which were select based on their affinity for human hair keratin solution as shown by Matrix-Assisted Laser-Desorption Ionization Time-of-Flight Mass Spectrometry (MALDI-TOF/TOF) and by molecular dynamics simulation. The peptides were characterized in detail regarding their ability to act as hair straightening modulators and to improve the tensile strength and elasticity of hair. Of the eight tested peptides, PepE, PepG and KP showed the highest ability to interact with a keratin peptide model, and to improve hair mechanical properties and straightening efficiency. The proposed solutions presented here will replace harsh reducing agents at alkaline pH by peptide formulations acting at neutral pH to change hair shape through the re-conformation of disulphide bonds. Here, we provide experimental evidence which explains at a molecular level how keratin decapeptides can interact with large keratin molecules in human hair, opening an innovative green approach to changing the shape of hair fibre.