In the field of prebiotic chemistry, hydrogen cyanide (HCN)-derived polymers have been studied for many years as a possible source of the precursors that provide the building blocks for proteins as well as nucleic acids, and they have also been associated with the origin of life. The HCN trimer, aminomalononitrile (AMN), polymerizes to give a brown complex nitrogenous polymer. We report the one-step polymerization-deposition of AMN as a simple generic surface-coating method and as an application of prebiotic chemical research to material science. We found that this polymerization, carried out in buffered aqueous solutions, can be used to coat a wide range of organic and inorganic substrate materials. The robust, non-cytotoxic coatings also provide for excellent cell attachment, suggesting potential biomedical applications. Furthermore, the coating chemistry allows for the immobilization of other compounds, including metals, both during coating formation or by performing secondary immobilization reactions.