The applications of norbornene or nadic end-capped high performance polymers (HPPs) are manifold and have been discussed in the literature for more than two decades. The cross-links formed from nadic end-cap determine the mechanical and thermal properties of these polymers. In spite of extensive studies, the cross-link structure and the cross-linking mechanism of nadic end-capped polymers remain elusive. Quantum chemical computations together with microkinetic modeling are used here to elucidate these aspects. Various possible polymerization pathways that contribute to the final cross-link structure of nadic end-capped polymers are proposed, and the distribution of cross-link structures is computed. The cross-linking mechanisms are modeled considering radical initialization, chain propagation, and termination, and our computations identify the most active cross-linking mechanism. The results of our study are then compared with the available experimental data.