(Chemical Equation Presented) Mucins are heavily glycosilated proteins that exhibit a broad range of adhesive interactions with various hydrophobic organic materials. However, there has been no clear evidence that mucins are capable of promoting chemical reactions. Here we provide the first demonstration that bovine submaxillary mucin and porcine gastric mucin accelerate the rate of fatty acid p-nitrophenol ester hydrolysis up to 337 times and a carbon-carbon bond-forming Diels-Alder reaction between N-propylmaleimide and anthracene up to 200 times relative to the rates of the reference processes, which were performed in water and chloroform, respectively. The discovered property of mucins to accelerate organic reactions provides a new and unique example of natural nonenzymatic proteins capable of promoting reactions of hydrophobic materials in aqueous solution. A better understanding of the interactions of mucins with hydrophobic molecules is needed for the development of superior drug-delivery systems and implantable devices.