Dipeptides are known to spontaneously cyclize to diketopiperazines, and in some cases these cyclic dipeptides have been shown to self‐assemble to form supramolecular nanostructures. Herein, we demonstrate the in situ cyclization of dipeptide methyl esters in aqueous buffer by intramolecular aminolysis, leading to the formation of diverse supramolecular nanostructures. The chemical nature of the amino acid side chains dictates the supramolecular arrangement and resulting nanoscale architectures. For c[LF], supramolecular gels are formed, and the concentration of starting materials influences the mechanical properties of these hydrogels. Moreover, by adding metalloporphyrins to the starting dipeptide starting solution, these become incorporated through cooperative assembly, resulting in the formation of nanofibers able to catalyse the oxidation of organic phenol in water. The approach taken here, which combines chemically activated assembly with the versatility of short peptides, demonstrates a new and easy method to achieving spontaneous formation of a variety of functional supramolecular materials using simple building blocks.