We propose here a new method to functionalize carbon materials via a catalyzed Diels–Alder reaction. In a Diels–Alder reaction, carbon materials can be used as a diene or a dienophile. Here, carbon materials are used as dienes and alkyne-terminated derivatives as dienophiles. Different carbon materials, i.e., glassy carbon, carbon powder (carbon black), pyrolytic graphite carbon materials, and graphene, were functionalized by alkyne ferrocene derivatives or perfluoro-tagged alkyne molecules and characterized by electrochemical means, atomic force microscopy, and X-ray photoelectron spectroscopy experiments. This method allows for the rapid functionalization of carbon materials in mild conditions with high surface coverage.