This review focuses on recent advances in the development of functionalizable antifouling coatings and their applications in label-free optical biosensors. Approaches to the development of antifouling coatings, ranging from self-assembled monolayers and PEG derivatives to ultra-low-fouling polymer brushes, are reviewed. Methods of preparation and characterization of antifouling coatings and the functionalization of antifouling coatings with bioreceptors are reviewed, and the effect of functionalization on the fouling properties of biofunctional coating is discussed. Special attention is given to biofunctional coatings for label-free bioanalysis of blood plasma and serum for medical diagnostics.