Over the past century, the radical thiol-ene reaction has demonstrated great value for the controlled synthesis of polymers and functionalized materials and for biomolecule conjugation. The free radical aspect offers many advantages, the three most prominent being water compatibility, a metal-free protocol (useful for the development of new therapeutic bioconjugates), and a bioorthogonal mode of action. This chapter covers recent developments in the use of the free radical thiol-ene “click” reaction for the synthesis and modification of biomolecules, bioconjugates, and biomaterials. Applications in peptide and protein science are also discussed, including major contributions to the synthesis of glycopeptides and lipopeptides as well as peptide stapling and cyclization. The various synthetic strategies towards thiosugars, glycoconjugates, and glycoclusters are also highlighted with a focus on the regio- and stereoselectivity of the process. An overview of the thiol-ene-mediated cross-linking strategy for the development of hydrogel biomaterials is also included, which demonstrates the diversity and versatility of the reaction in a biomolecular context.