There is a significant conceptual difference in the mode of action of the catalysts found in nature, that is, the enzymes, and most of the catalysts are traditionally designed and employed for organic synthesis. In recent years, a variety of peptide-based catalysts that display some of the qualities of enzyme conversions have been developed. Proline-based organocatalysts were developed by combinatorial selection from moderately active proline catalysts for the aldol family of reactions to a highly efficient peptide catalyst for selective 1,4-Michael additions. While organocatalysis with peptide-based catalysts can provide excellent activity and selectivity in biomimetic reactions, including acylations, phosphorylations, oxidations, and brominations with efficiencies approaching those of the natural enzymes, the combination of peptide templates with coordination of transition metals opens up entirely new opportunities. The peptidic nature of the catalysts described in this chapter opens up new opportunities for catalysis due to their structural resemblance with bioderived peptides.