In biological systems, disulfide bonds are formed efficiently under mild conditions without the release of harmful byproducts. Inspired by nature, we report a biomimetic polydopamine (PDA) catalyst for oxidative thiol coupling. This reaction was accelerated with only a small amount of PDA particles in neutral, weakly alkaline, and even weakly acidic aqueous media at room temperature under an air atmosphere. The catalytic particles were facilely separated and were reused without a decrease in activity. The entire process is totally biofriendly, including the synthesis of the PDA particles. This route is especially useful for the synthesis of pharmaceutical molecules.