Polydicyclopentadiene (PDCPD) is a tough, heavily crosslinked thermoset polymer that has high heat, chemical, and impact resistance coupled with a low density. Current limitations to the broader industrial application of PDCPD include its low surface energy and lack of chemical tunability. Here, we report the first example of a polymer derived from a carboxyl-functionalized dicyclopentadiene monomer and its subsequent thermal crosslinking. The resulting material has the highest glass-transition temperature reported for a polydicyclopentadiene and allows for the facile manipulation of the surface chemistry through alteration of the embedded functional group. We also report the first observation by differential scanning calorimetry of the crosslinking step as a discreet thermal event.