Polyester dominates the world fiber market and is used in almost all applications due to its versatile properties and low price. Nevertheless, it has low wettability and high electrostatic charge, which are overcome by partly environmentally harmful hydrophilic/antistatic finishing agents or caustic treatments. Additionally, polyester irreversibly accumulates in the environment as the processing, and the use of textiles made of synthetic polymers is a significant source of fibrous microplastic. As polyesterases degrade the ester bonds of polyesters, leading to free carboxyl and hydroxyl groups, enzyme technology offers extensive potential in industrial polyester finishing processes. Likewise, no vast quantities of chemicals are needed, resulting in a relatively low environmental impact. However, this fundamental understanding has not yet been fully implemented in the industry. Research in the field of polyester-degrading enzymes has found several new microorganisms and enzymes that are capable of attacking the ester bonds of synthetic polyester. Still, these “1st generation” enzymes are not effective enough for industrial needs. A solution is the development of next-generation polyesterases with adapted properties so that biotechnical surface modification, as well as degradation of polyester to recover valuable building blocks, can become economically feasible. The enzymes available on the market were investigated and applied in laboratory tests on both yarns and textile surfaces. The commercially available enzymes tested were not found to be effective enough to functionalize the materials with any measurable effect. However, the 2nd generation enzymes did: the tests showed an improved surface functionality. The best enzymatic treatments were achieved already after a few hours at an optimum use of neutral pH value and moderate temperature. The functional groups were primarily detected via the methylene blue test. The Ninhydrin test confirmed the successful removal of enzymes by washing the textiles after the enzymatic treatment. PET yarn with a low degree of crystallinity was completely degraded within only several days, while stretched filaments showed a low level of functionalization. All in all, 2nd generation polyesterases can be integrated into an optimized enzymatic treatment process of (amorphous) polyester, regardless of origin, to generate functional groups on the fiber surface for an innovative approach of functionalization, which may be able to replace chemical-intensive processes in the textile industry in the future.