The self‐assembly of small molecules into supramolecular polymers can be analogous to the formation of classical solid‐state crystals depending on the mechanism of polymerization. Taking inspiration from the field of materials science, complex supramolecular polymer nanostructures can be formed by carefully controlling nucleation and growth processes. Exploration of the energy landscapes in supramolecular polymers can also lead to the discovery of polymorphs where a single monomer can self‐assemble into different supramolecular polymers with distinct molecular packing arrangements. This mini‐review focuses on recent developments where the manipulation of nucleation and growth processes were used to develop novel supramolecular copolymers and explore polymorphism in supramolecular materials, highlighting examples of such systems composed of small organic molecules and peptides. © 2022 The Authors. Polymer International published by John Wiley & Sons Ltd on behalf of Society of Industrial Chemistry. This review highlights recent developments in the use of nucleation and growth processes to develop novel supramolecular block copolymers and explore polymorphism in supramolecular materials.