Peptide based hydrogels have received much attention due to their potential biomedical applications. The majority of the gel forming peptides present a β-sheet motif that is composed of alternating hydrophobic/hydrophilic amino acids. Furthermore, structural characterization of the assembly of these β-sheet peptides has been refined recently. However, the relationship between peptide residue composition, molecular structure and the mechanical properties of the resulting hydrogel is not entirely understood. In this review, an analysis of the structural features of different β-sheet peptide hydrogels and their mechanical properties is discussed, in order to provide further insight on the molecular features that are relevant for the design of effective β-peptide hydrogels.